Child Support Registrar v CMU23

1. The terms of order 2 of the orders of 21 November 2023 be extended to any affidavit filed in these proceedings, having regard to s 150 of the Child Support (Assessment) Act 1989 (Cth).
2. The appeal be allowed.
3. The decision of the Administrative Appeals Tribunal (Tribunal) of 14 September 2023 be set aside and the matter remitted to the Tribunal for review decision according to law.
4. There be no order as to costs. Note: Entry of orders is dealt with in Rule 39.32 of the Federal Court Rules 2011.

LOGAN J: 1 Section 3 of the Child Support (Assessment) Act 1989 (Cth) (the Assessment Act) contains a Parliamentary statement in respect of the duty of parents to maintain their children. It provides: Duty of parents to maintain their children (1) The parents of a child have the primary duty to maintain the child. (2) Without limiting subsection (1), the duty of a parent to maintain a child: (a) is not of lower priority than the duty of the parent to maintain any other child or another person; and (b) has priority over all commitments of the parent other than commitments necessary to enable the parent to support: (i) himself or herself; and (ii) any other child or another person that the parent has a duty to maintain; and (c) is not affected by: (i) the duty of any other person to maintain the child; or (ii) any entitlement of the child or another person to an income tested pension, allowance or benefit. 2 In turn, s 4(1) of the Assessment Act provides that the principal object of the Act is to ensure that children receive a proper level of financial support from their parents. 3 The duty of parents to maintain their children, and the ensuring that children receive a proper level of financial support from their parents, are no new subjects. In the Commonwealth's first legislative foray into the field of matrimonial causes, the Matrimonial Causes Act 1959 (Cth), s 84 of that Act, as enacted, was directed to the subject of, amongst other things, the maintenance of children of a marriage. That section provided: 84.(1.) Subject to this section, the court may, in proceedings with respect to the maintenance of a party to a marriage, or of children of the marriage, other than proceedings for an order for maintenance pending the disposal of proceedings, make such order as it thinks proper, having regard to the means, earning capacity and conduct of the parties to the marriage and all other relevant circumstances. (2.) Subject to this section and to the rules, the court may, in proceedings for an order for the maintenance of a party to a marriage, or of children of the marriage, pending the disposal of proceedings, make such order as it thinks proper, having regard to the means, earning capacity and conduct of the parties to the marriage and all other relevant circumstances. (3.) The court may make an order for the maintenance of a party notwithstanding that a decree is or has been made against that party in the proceedings to which the proceedings with respect to maintenance are related. (4.) The power of the court to make an order with respect to the maintenance of children of the marriage shall not be exercised for the benefit of a child who has attained the age of twenty-one years unless the court is of opinion that there are special circumstances that justify the making of such an order for the benefit of that child. 4 The elegant simplicity of s 84 of the Matrimonial Causes Act stands in marked contrast to the convoluted and Byzantine provisions which have, for some reason or other, commended themselves to Parliament and are presently found in the Assessment Act. It was put - and rightly so, with respect - in submissions that the provisions of the Assessment Act are complex. That they certainly are. It must be very difficult indeed for the Child Support Registrar (Registrar), who has day-to-day administration of the Act, to administer that Act. It must be even more difficult for those Australians who have, for one reason or another, occasion to look to and be subject to that Act to understand the nature and extent of their liabilities. 5 Our society is governed by the rule of law, but such governance is put in jeopardy when legislation becomes so complex as not readily to admit of administration by ordinary, good, honest civil servants or ready comprehension of ordinary Australians of average intelligence. This particular appeal truly gives one pause for thought about whether we have, in any meaningful way, progressed or, rather, regressed, when one compares the Assessment Act with the drafting style that once commended itself to what the Constitution terms the Queen's Ministers of State for the Commonwealth, and, in turn, given Ministerial responsibility, to Parliament. There must come a time, surely, when Ministers of State discharging their duty, or, if they do not, Parliament, reject out of hand drafting of the present kind that is presented to them by those in public administration for approval. 6 All that said, it is necessary, in the discharge of judicial duty, and in the context of the present appeal, to determine whether or not, having regard to the grounds of appeal, there has been an error of law, as alleged, by the Administrative Appeals Tribunal (Tribunal) on a review of a child support controversy. The controversy is one of law, not fact. 7 The background facts are recited in the reasons of the Tribunal. In reciting the facts and having regard to s 150 of the Assessment Act, it is necessary to afford anonymity to the particular parents and children in respect of whom the child support controversy arose. In keeping with the need for such anonymity, the facts then are as follows. 8 The first respondent (CMU23) and the second respondent (CMV23) were at all material times parties to a child support case registered with "Services Australia" - the child support agency (Child Support) from 12 April 2007, in relation to financial support to be provided for Master J (born in 2007) and Miss M (born in 2004) ("the children"). The application which came to the Tribunal for the review concerned the percentages of care to be recorded for each of the first respondent and the second respondent, and in turn, used in the calculation of the child support payable in relation to two changes to the care position of the children. 9 The first care change occurred on 6 February 2019. The second care change occurred on 29 January 2020. 10 In respect of the first care change, the issue before the Tribunal was from when percentages of care of 0% to the first respondent and 100% to the second respondent in relation to a change in the actual care of the children from 6 February 2019, notified to Child Support on 9 February 2022, apply; rather then the previously recorded percentages of care of 35% to the first respondent and 65% to the second respondent, previously occurring and applying pursuant to a court order dated 20 May 2009. 11 As apprehended by the Tribunal, it was necessary to consider whether s 53(1)(c) of the Assessment Act was to be construed such that it prevented the operation of s 51 of that Act. The latter, as the Tribunal understood it (see, [4] of the Tribunal's reasons), allowed an interim period, during which care that was to occur under a care arrangement continued to be recorded for a specified period, in certain circumstances, despite care no longer actually occurring pursuant to that care arrangement. 12 The question the Tribunal posed for itself, in relation to the first care change, was that: If the answer to that question is that paragraph 53(1)(c) does not prevent such an interim period, applying pursuant to section 51, the question then arises as to whether section 51 can apply when the change to care is notified after the end of the maximum interim period that could possibly apply. 13 At [4] of the reasons, the Tribunal posed a consequential question, namely: Finally, if the answer to that question is that section 51 can still apply (and does apply), the question arises as to what the dates of application are for the new percentage of care determinations. 14 The submissions made to the Tribunal as to the answers to these questions, as recorded in [5] of the Tribunal's reasons, were as follows: 5 The various different submissions of the parties are as follows: (a) [first respondent] submits that he should continue to be recorded with a percentage of care of 35% until 6 August 2019, with 0% then applying for him from 7 August 2019 and that [second respondent] should continue to be recorded with a percentage of care of 65% until 8 February 2022 with 100% then applying for [second respondent] from 9 February 2022 in relation to the 6 February 2019 change in care; (b) Child Support's original decision (on 26 July 2022) was that, following the application of an interim period when care continued to be recorded as previously, from 7 August 2019 a percentage of care of 0% applies for [first respondent] and a percentage of care of 100% applies for [second respondent]; and (c) Child Support's now position (4 August 2023 submissions) is that an interim period cannot apply and that [first respondent's] pre-existing percentage of care determination of 35% is revoked from 5 February 2019 and [second respondent's] pre-existing percentage of care determination of 65% is revoked from 8 February 2022. It is not clear from Child Support's submissions, but this presumably has the consequential effect that the then new percentage of care determinations of 0% for [first respondent] and 100% for [second respondent] apply from 6 February 2019 and 9 February 2022 respectively. 15 The Tribunal answered the question in a summary way in [6] of its reasons, for reasons which were then the subject of great elaboration later in the reasons. In respect of the first care period, the Tribunal stated in [6]: 6 For the Reasons that follow, the Tribunal's conclusion in relation to the questions posed are that 1) paragraph 53(1 )(c) does not prevent the possible application of section 51, 2) section 51 can still apply if notification of the change in care occurs after the end of the maximum interim period that could apply and 3) section 54C applies such that percentage of care determinations of 35% for [first respondent] and 65% for [second respondent] apply until 6 August 2019, with 0% then applying for [first respondent] and 100% then applying for [second respondent] from 7 August 2019. This accords with the original decision of Child Support. [footnote references omitted] 16 In respect of the second care change, the controversy as recited by the Tribunal, the submissions of the parties and the Tribunal's resolution thereof was as follows: 7 At issue is from when percentages of care of 14% to [first respondent] and 86% to [second respondent] in relation to a further change in the actual care of the children from 29 January 2020, of which Child Support became aware on 1 December 2021, apply, rather than the previously recorded percentages of care. 8. The various different submissions of the parties are as follows: (a) [first respondent] had no particular submissions to make as regards the date of effect of the new percentage of care determinations in relation to the 29 January 2020 change in care, other than his overall submission that [second respondent] should not be in a better position, via application of the interim care period, than she would have been otherwise with 100% care not applying for her until 9 February 2022; (b) Child Support's original decision (on 26 July 2022) was that, following a change to the percentage of care determination of 0% for [first respondent] and the percentage of care determination of 100% for [second respondent] from 7 August 2019 (in relation to the 6 February 2019 change in care), a further change in care occurred on 29 January 2020 with a new percentage of care determination of 14% applying for [first respondent] from 1 December 2021 and a new percentage of care determination of 86% applying for [second respondent] from 29 January 2020; and (c) Child Support's now position (4 August 2023 submissions) is the same; that is, that a new percentage of care determination of 14% applies for [first respondent] from 1 December 2021 and a new percentage of care determination of 86% applies for [second respondent] from 29 January 2020. 9. For the Reasons that follow, the Tribunal's conclusion is that a percentage of care determination of 14% applies for [first respondent] from 1 December 2021 and a percentage of care determination of 86% applies for [second respondent] from 29 January 2020. This accords with the original decision of Child Support. [footnote references omitted] 17 Further detail concerning the factual background to the review proceeding before the Tribunal was supplied in the Tribunal's reasons (see [10] to [24]), but it is not necessary, for the purpose of resolving the appeal, to detail this. 18 Although they have been served both with the notice of appeal and the Registrar's submissions, and the notice of hearing, neither the first nor the second respondent has taken any active part in the hearing of the appeal. 19 As posed in the notice of appeal, the question of law is as follows: 1. On the proper construction of paragraph 53(1)(c) of the Child Support (Assessment) Act 1989 (Cth) (Act), does section 51 of that Act apply to a (new) determination of a responsible person's percentage of care required to be made under section 49(1)(b) or 50(1)(b) of the Act following the revocation under section 54F or 54H of the Act of the (existing) percentage of care determination for that responsible person? 20 I am quite satisfied that this does indeed state a question of law. 21 The Registrar's grounds of appeal are as follows: 1. The Tribunal erroneously applied section 51 of the Act to determinations of percentage of care for the Respondents because it misconstrued paragraph 53(1)(c) of the Act. a. The Tribunal found that, following a change of care on 6 February 2019, it was required to: i. revoke the First Respondent's existing determination of percentage of care under section 54F of the Act, and make a new determination of percentage of care for the First Respondent under section 49(1)(b) of the Act; and ii. revoke the Second Respondent's existing determination of percentage of care under section 54F of the Act, and make a new determination of percentage of care for the Second Respondent under section 50(1)(b) of the Act. b. By reason of the matters set out in paragraph 1.a, when the new determinations were required to be made, each Respondent was a responsible person in relation to whom a determination was to be and had been made, and in relation to whom a determination had been revoked under section 54F of the Act, within the meaning of paragraph 53(1)(c) of the Act. c. By reason of the matters set out in paragraph 1.b, s 53(1)(c), properly construed, meant that section 51 did not apply to the new determination to be made for each Respondent. d. The Tribunal erred by construing paragraph 53(1)(c) of the Act as not disapplying section 51 to the new determination to be made for each Respondent. 22 Resolving the question of law on the grounds stated requires that a number of provisions of the Assessment Act be set out. It is desirable, before setting out those provisions, and by way of introduction, to set out two "simplified outlines". The first is found in s 35A of the Assessment Act. That offers a "simplified outline" in respect of Part 5. It provides: • This Part includes the formulas used for assessing the annual rate of child support payable by a parent for a child for a day in a child support period (other than in cases where that rate is worked out in accordance with a child support agreement, a Registrar's determination under Part 6A or a court order). • The Costs of the Children Table published by the Secretary each year (based on the table in Schedule 1 to this Act) sets out the costs to parents of raising children in various age ranges. • Those costs are to be met by both parents (by paying child support or by caring for their children) according to each parent's capacity to meet the costs. • To determine each parent's capacity to meet those costs, the parents are assessed in respect of the costs of the child. • Generally, both parents' income is taken into account in determining each parent's capacity to meet the costs of their children. • The formulas also allow child support payable to non-parent carers of children to be worked out. 23 In turn, s 48 of the Assessment Act offers a "simplified outline" of Division 4 of Part 5. It provides: • A responsible person's percentage of care for a child during a care period is the percentage of care determined by the Registrar under Subdivision B of this Division. • A responsible person's percentage of care for a child is used in section 55C to work out the responsible person's cost percentage for the child. 24 This appeal is concerned with particular provisions within Division 4 of Part 5 of the Assessment Act. Within Division 4, section 49 provides: Determination of percentage of care--responsible person has had etc. no pattern of care for a child (1) This section applies if: (a) either of the following applies: (i) an application is made under section 25 or 25A for a parent to be assessed in respect of the costs of the child; (ii) a parent is taken under section 73A to have had a relevant dependent child from a day specified in that section; and the Registrar is satisfied that a responsible person for the child has had, or is likely to have, no pattern of care for the child during such period (the care period ) as the Registrar considers to be appropriate having regard to all the circumstances; or (b) both of the following apply: (i) the determination of a responsible person's percentage of care for a child that was made under this section or section 50 is revoked or suspended under Subdivision C of this Division, except under paragraph 54FA(3)(b) or 54HA(3)(b); (ii) the Registrar is satisfied that the responsible person has had, or is likely to have, no pattern of care for the child during such period (the care period ) as the Registrar considers to be appropriate having regard to all the circumstances. (2) The Registrar must determine the responsible person's percentage of care for the child during the care period. (3) The percentage of care determined under subsection (2) must be 0%, unless section 51 applies in relation to the responsible person. 25 Section 50 provides: Determination of percentage of care--responsible person has had etc. a pattern of care for a child (1) This section applies if: (a) either of the following applies: (i) an application is made under section 25 or 25A for a parent to be assessed in respect of the costs of the child; (ii) a parent is taken under section 73A to have had a relevant dependent child from a day specified in that section; and the Registrar is satisfied that a responsible person for the child has had, or is likely to have, a pattern of care for the child during such period (the care period) as the Registrar considers to be appropriate having regard to all the circumstances; or (b) both of the following apply: (i) the determination of a responsible person's percentage of care for a child that was made under section 49 or this section is revoked or suspended under Subdivision C of this Division, except under paragraph 54FA(3)(b) or 54HA(3)(b); (ii) the Registrar is satisfied that the responsible person has had, or is likely to have, a pattern of care for the child during such period (the care period) as the Registrar considers to be appropriate having regard to all the circumstances. (2) The Registrar must determine the responsible person's percentage of care for the child during the care period. (3) The percentage determined under subsection (2) must be a percentage that corresponds with the actual care of the child that the Registrar is satisfied that the responsible person has had, or is likely to have, during the care period. (4) Subsection (3) does not apply if section 51 applies in relation to the responsible person. 26 Section 51 provides: Percentage of care if action taken to ensure that a care arrangement in relation to a child is complied with (1) This section applies if: (a) the Registrar is required by section 49 or 50 to determine a responsible person's percentage of care for a child during a care period; and (b) a care arrangement applies in relation to the child; and (c) the Registrar is satisfied that the actual care of the child that the responsible person has had, or is likely to have, during the care period does not comply with the extent of care of the child that the person should have had, or is to have, under the care arrangement during that period (which may be nil); and (d) a person who has reduced care of the child is taking reasonable action to ensure that the care arrangement is complied with. Note: This section does not apply in certain circumstances: see section 53. 2 percentages of care in relation to the responsible person (2) Subject to subsection (5), the Registrar must determine, under section 49 or 50, 2 percentages of care in relation to the responsible person. (3) The first percentage of care is to be a percentage that corresponds with the extent of care of the child that the responsible person should have had, or is to have, under the care arrangement during the care period (which may be nil). (4) The second percentage of care is to be: (a) for a determination under section 49 - 0%; or (b) for a determination under section 50-a percentage that corresponds with the actual care of the child that the Registrar is satisfied that the responsible person would be likely to have during the care period if the action referred to in paragraph (1)(d) were not to succeed. Single percentage of care in relation to the responsible person (5) If the Registrar is satisfied that special circumstances exist in relation to the child, the Registrar may determine, under section 49 or 50, a single percentage of care in relation to the responsible person. (6) The single percentage of care is to be: (a) for a determination under section 49 - 0%; or (b) for a determination under section 50 - a percentage that corresponds with the actual care of the child that the Registrar is satisfied that the responsible person would be likely to have during the care period if the action referred to in paragraph (1)(d) were not to succeed. 27 Section 53 provides: Section 51 does not apply in certain circumstances (1) Section 51 does not apply in relation to a responsible person in relation to whom a determination is to be or has been made under section 49 or 50 if: (a) in a case where subparagraph 49(1)(a)(i) or 50(1)(a)(i) applies in relation to the determination--the day the application referred to in that subparagraph is made is after the end of the maximum interim period for the determination; or (b) in a case where subparagraph 49(1)(a)(ii) or 50(1)(a)(ii) applies in relation to the determination--the day referred to in that subparagraph is after the end of the maximum interim period for the determination; or (c) the Registrar has revoked the determination under section 54F or 54H. (2) Section 51 also does not apply in relation to a responsible person in relation to whom a determination (a later determination) has been made under section 49 or 50 if: (a) an earlier determination determined the responsible person's percentage of care for a child under that section for the purposes of subsections 51(3) and (4); and (b) the later determination is made after the end of the maximum interim period for the earlier determination; and (c) the later determination relates to the same care arrangement as the earlier determination. 28 The meaning of "interim period" is supplied by s 53A. It is not necessary to set out the dense thicket that reposes in s 53A. 29 Section 54F provides: Determination must be revoked if there is a change to the responsible person's cost percentage (1) The Registrar must revoke a determination of a responsible person's percentage of care (the existing percentage of care) for a child made under section 49 or 50 if: (a) the Registrar or Secretary is notified, or otherwise becomes aware, that the care of the child that is actually taking place does not correspond with the responsible person's existing percentage of care for the child; and (b) the Registrar is satisfied that the responsible person's cost percentage for the child would change if the Registrar were to determine, under section 49 or 50, another percentage to be the person's percentage of care for the child; and (c) section 54G does not apply; and (d) subsection (2) applies in relation to the individual. Note: The Registrar must make another determination under section 49 or 50 to replace the revoked determination: see paragraph 49(1)(b) or 50(1)(b). (2) This subsection applies in relation to a responsible person if: (a) disregarding paragraph 53(1)(c), section 51 did not apply in relation to the responsible person; or (b) section 51 did apply in relation to the responsible person but the maximum interim period for the determination has ended; or (c) all of the following apply: (i) section 51 did apply in relation to the responsible person; (ii) the maximum interim period for an earlier determination of the responsible person's percentage of care for the child has not ended; (iii) an interim period does not currently apply in relation to the earlier determination; (iv) the determination referred to in subsection (1) was made while the earlier determination was suspended under this Subdivision. Note: For when section 51 does not apply, see section 53. (3) The revocation of the determination takes effect at the end of: (a) if the Registrar or Secretary is notified, or otherwise becomes aware, of the matter referred to in paragraph (1)(a) within 28 days after the change of care day for the responsible person--the day before the change of care day; or (b) if the Registrar or Secretary is notified, or otherwise becomes aware, of that matter more than 28 days after the change of care day for the responsible person and: (i) the responsible person's care of the child has increased--the day before the Registrar or Secretary is notified, or otherwise becomes aware, of that matter; or (ii) the responsible person's care of the child has reduced--the day before the change of care day. 30 Section 54H provides: Registrar may revoke a determination of a responsible person's percentage of care (1) The Registrar may revoke a determination of a responsible person's percentage of care (the existing percentage of care) for a child made under section 49 or 50 if: (a) the Registrar or Secretary is notified, or otherwise becomes aware, that the care of the child that is actually taking place does not correspond with the responsible person's existing percentage of care for the child; and (b) the Registrar is satisfied that, if the Registrar were to determine, under section 49 or 50, another percentage to be the responsible person's percentage of care for the child, the other percentage would not be the same as the person's existing percentage of care for the child; and (c) sections 54F, 54FA and 54G do not apply; and (d) subsection (2) applies in relation to the individual. Note: The Registrar must make another determination under section 49 or 50 to replace the revoked determination: see paragraph 49(1)(b) or 50(1)(b). (2) This subsection applies in relation to a responsible person if: (a) disregarding paragraph 53(1)(c), section 51 did not apply in relation to the responsible person; or (b) section 51 did apply in relation to the responsible person but the maximum interim period for the determination has ended; or (c) all of the following apply: (i) section 51 did apply in relation to the responsible person; (ii) the maximum interim period for an earlier determination of the responsible person's percentage of care for the child has not ended; (iii) an interim period for the earlier determination does not currently apply; (iv) the determination referred to in subsection (1) was made while the earlier determination was suspended under this Subdivision. Note: For when section 51 does not apply, see section 53. (3) The revocation of the determination takes effect at the end of: (a) if the Registrar or Secretary is notified, or otherwise becomes aware, of the matter referred to in paragraph (1)(a) within 28 days after the change of care day for the responsible person - the day before the change of care day; or (b) if the Registrar or Secretary is notified, or otherwise becomes aware, of that matter more than 28 days after the change of care day for the responsible person and: (i) the responsible person's care of the child has increased - the day before the Registrar or Secretary is notified, or otherwise becomes aware, of that matter; or (ii) the responsible person's care of the child has reduced - the day before the change of care day. 31 The provisions found in Div 4 of Pt 5 in turn inform how, pursuant to s 55C of the Assessment Act, found in Div 5 of Pt 5, cost percentages are worked out. It is not necessary to set out s 55C, only to note that the percentage of care is relevant to the statutory formula found in s 55C. A feature of that formula flowing from the provisions of Div 4 of Pt 5 is that, in general, the higher a person's "percentage of care", the less child support they are required to pay. 32 In this case, there were determinations which, on the face of s 53(1)(c) of the Assessment Act, one might have thought led inexorably to the non-application of s 51 of the Assessment Act. As is apparent from the Tribunal's reasons, the Registrar had something of a change of heart in the course of the proceedings before the Tribunal, as to whether or not s 53 of the Assessment Act did indeed have that operation. I observe at once that no criticism of the Registrar is intended by my use of the phrase "change of heart". As already observed, this is complex legislation. Further, as will become apparent, there is a discordance of views in the Tribunal as to the meaning of s 53(1)(c) and its effect on the application of s 51. It is just one of those cases where it appears that the discipline of having to make a considered submission to the Tribunal on the construction of the Assessment Act has led the Registrar to form a settled view that s 53 renders, in the circumstances of the present case, s 51 in applicable. 33 Such openness in the face of an apparent statutory construction inhibition to a change of views on the part of an official charged with public administration of an Act is to be commended, not the subject of adverse criticism. 34 However that may be, it transpired that the Tribunal preferred the Registrar's original, rather than later promoted, construction of the Assessment Act. It is apparent from the Tribunal's reasons that the Tribunal regarded the present as a case where there was an anomaly or absurdity in the text of s 53(1)(c) of the Assessment Act, such that it was open to the Tribunal, in terms of statutory construction principle, to imply or supply particular additional words into s 53(1)(c). It is also apparent from the Tribunal's reasons that, in reaching that view, the Tribunal was informed by statements in the explanatory memorandum to the bill, which became an amendment to the Assessment Act which inserted s 53 in its present form. 35 The reasons of the Tribunal for adopting this course are detailed. It would do less than justice to the effort made by the Member constituting the Tribunal to make sense of the Assessment Act to do other than now cite an extract from the Tribunal's reasons which offers that detail: 43. The Tribunal had regard to a number of matters in interpreting paragraph 53(1)(c), including the Child Support Registrar's submissions, for the purposes of ascertaining whether section 51 can apply in the circumstances of the 6 February 2019 care change. 44. Relevantly, sections 15AA and 15AB of the Acts Interpretation Act 1901 (the AI Act), 'a dictionary and manual to use when reading and interpreting Commonwealth Acts and instruments made under Commonwealth Acts' (section 1A), provide as follows in relation to statutory interpretation: Section 15AA Interpretation best achieving Act's purpose or object In interpreting a provision of an Act, the interpretation that would best achieve the purpose or object of the Act (whether or not that purpose or object is expressly stated in the Act) is to be preferred to each other interpretation. Section 15AB Use of extrinsic material in the interpretation of an Act (1) Subject to subsection (3), in the interpretation of a provision of an Act, if any material not forming part of the Act is capable of assisting in the ascertainment of the meaning of the provision, consideration may be given to that material: (a) to confirm that the meaning of the provision is the ordinary meaning conveyed by the text of the provision taking into account its context in the Act and the purpose or object underlying the Act; or (b) to determine the meaning of the provision when: (i) the provision is ambiguous or obscure; or (ii) the ordinary meaning conveyed by the text of the provision taking into account its context in the Act and the purpose or object underlying the Act leads to a result that is manifestly absurd or is unreasonable. (2) Without limiting the generality of subsection (1), the material that may be considered in accordance with that subsection in the interpretation of a provision of an Act includes: … (e) any explanatory memorandum relating to the Bill containing the provision, or any other relevant document, that was laid before, or furnished to the members of, either House of the Parliament by a Minister before the time when the provision was enacted; … 45. The Tribunal first had regard to the actual wording of paragraph 53(1)(c), which is: (1) Section 51 does not apply in relation to a responsible person in relation to whom a determination is to be or has been made under section 49 or 50 if: (a) in a case where subparagraph 49(1)(a)(i) or 50(1)(a)(i) applies in relation to the determination-the day the application referred to in that subparagraph is made is after the end of the maximum interim period for the determination; or (b) in a case where subparagraph 49(1)(a)(ii) or 50(1)(a)(ii) applies in relation to the determination-the day referred to in that subparagraph is after the end of the maximum interim period for the determination; or (c) the Registrar has revoked the determination under section 54F or 54H. 46. As has already been noted, the scheme of the Act as it relates to the recording of percentage of care determinations for child support purposes, is that initial percentage of care determinations are made upon initial registration of a child support case and generally then existing percentage of care determinations are required to be revoked before new percentage of care determinations reflecting changed care can apply. 47. Revocation of pre-existing percentage of care determinations can only occur pursuant to section 54F, 54G or 54H of the Act. Broadly speaking, those provisions provide for revocation in the following circumstances: (a) Section 54G - requires mandatory revocation of a pre-existing percentage of care determination in relatively narrow circumstances, including when a person was to have at least 14% care of a child and they are having less than 14% care despite the child being made available for care. (b) Section 54F - requires mandatory revocation of a pre-existing percentage of care determination when section 54G does not apply, the care that is actually taking place does not correspond with the pre-existing percentage of care determination and a change to the percentage of care determination would alter the cost percentage used in the administrative assessment of child support. (c) Section 54H - allows discretionary revocation of a pre-existing percentage of care determination when sections 54F, 54FA and 54G do not apply, and the care that is actually taking place does not correspond with the pre-existing percentage of care determination (that is, a change to percentage of care determination is not required to have the effect of altering the cost percentage used in the formula for administrative assessment of child support, as is required by section 54F). 48. Section 51 generally makes provision for pre-existing percentage of care determinations to continue to be recorded for an interim period when a care arrangement (such as a court order or written parenting plan) is not being complied with and the person who is not having care as they should under the care arrangement is taking reasonable action to have it complied with. 49. The concept of a maximum interim period, introduced by 2018 amendments to the legislation, is an important concept to understand in the context of how the care provisions operate since the 2018 amendments. 50. The legislation provides for a maximum interim period (as defined in section 5) and an interim period. A maximum interim period is a set period unaffected by any action or inaction on the part of the parties to a child support case. An interim period will ordinarily have the same duration as a maximum interim period unless it is shortened. The maximum interim period may be shortened if a parent with increased care takes reasonable action to participate in family dispute resolution. However, a further interim period can apply if a shorter interim period has applied, the person with reduced care continues to take reasonable action for compliance with the care arrangement but the person with increased care ceases to take reasonable action to participate in family dispute resolution before the end of the maximum interim period. Therefore, a maximum interim period can comprise more than one interim period, but only if family dispute resolution is involved. 51. A 'quick' reading of paragraph 53(1)(c), that is 'Section 51 does not apply in relation to a responsible person in relation to whom a determination is to be or has been made under section 49 or 50 if ... the Registrar has revoked the determination under section 54F or 54H', might suggest that section 51 does not apply in the circumstances of this case because the Tribunal has determined that each of the pre-existing percentage of care determinations as at 6 February 2019, of 35% for [first respondent] and 65% for [second respondent], must be revoked pursuant to section 54F. However, more than a 'quick' read is warranted. The legislative provisions are complex and understandably so given the intricate nature of the purpose of the provisions. Section 53 cannot be read alone. All of the relevant legislative provisions need to be read together because of the interlinking between them as is necessary given their intricate nature. The interpretation now contended by Child Support is not consistent with the overall scheme of the legislation in relation to care. Section 51 is unlikely, if ever, to apply in relation to a section 54G revocation scenario because section 54G requires that care is being made available, a situation unlikely to exist when a care arrangement is being breached requiring action for compliance, the scenario underpinning section 51. Section 51 will therefore usually only have potential application in relation to section 54F or section 54H revocation situations such that to read paragraph 53(1)(c) as excluding situations where pre-existing percentage of care determinations are revoked pursuant to section 54F or 54H, as is now contended by the Registrar, would lead to the result that an interim period is unlikely, if ever, to apply once a child support case has commenced, an apparent inconsistency if not absurdity. 52. Where different possible interpretations are possible, pursuant to section 15AA of the AI Act, the preferred interpretation requires 'an interpretation that would best achieve the purpose or object of the Act (whether or not that purpose or object is expressly stated in the Act)'. Section 4 of the Act, states that the principal object of the Act is 'to ensure that children receive a proper level of financial support from their parents' with particular objects of the Act also specified. Minimal assistance is provided by recourse to the principal or particular objects of the Act for interpretation of a specific provision such as paragraph 53(1)(c). However, the Tribunal observes that the general purpose of the Act is consistent with an interim period, recognising care that should have occurred pursuant to a breached care arrangement for a limited time, applying in the appropriate circumstances. As already observed, it may be considered absurd if paragraph 53(1)(c) was interpreted in the manner now contended by the Child Support Registrar resulting in an interim period unlikely to ever apply. 53. The Tribunal also considered the Revised Explanatory Memorandum to the Family Assistance and Child Support Legislation Amendment (Protecting Children) Bill 2017, which led to the replacement of the then section 53, in considering whether it assists in ascertaining the intention of paragraph 53(1)(c), as is permitted by paragraph 15AB(1)(b) (and particularly subparagraph 15AB(1)(b)(ii)) and paragraph 15AB(2)(e) of the AI Act. 54. The Revised Explanatory Memorandum includes the following of relevance: Part 1 - Interim periods This Part amends the Child Support (Assessment) Act 1989 and the A New Tax System (Family Assistance) Act 1999 to extend the interim period that applies for recently-established court­ordered care arrangements and provides incentives for the person with increased care to take reasonable action to participate in family dispute resolution where a care dispute relates to an older court order, a parenting plan or a written agreement. … Item 25 inserts a new definition in subsection 5(1) for maximum interim period for the purposes of a determination under section 49 or 50. For a determination of a responsible person's percentage of care for a child under section 49 or 50, the maximum interim period that can apply begins on the change of care day (as defined in subsection 5(1)) and, for a determination relating to a court order, ends on the later of the period of 52 weeks starting on the day the court order first takes effect, or the end of the period of 26 weeks starting on the change of care day. For a determination relating to a written agreement or parenting plan, the maximum interim period ends at the end of the period of 14 weeks starting on the change of care day. Item 25 also inserts a signpost definition for the phrase takes reasonable action to participate in family dispute resolution. … Item 31 repeals section 52 as it is not consistent with the amendments in this Part, which seek to ensure that care arrangements are complied with. Section 52 allows for an interim period to apply where a parent is seeking a new care arrangement that would require less care than that provided in the existing arrangement, but greater than the extent of their actual care. It is not appropriate for the care arrangement to be reflected in a situation where both parties are seeking a different level of care. In such situations, it is more appropriate for actual care to be reflected. Item 31 also replaces section 53. New section 53 incorporates the concept of a "maximum interim period" rather than the 14-week interim period that is currently in section 53. Current subsection 53(1) provides that section 51 does not apply if certain events in relation to the determination of a responsible person's percentage of care for a child occur 14 weeks or more after the change of care day. New subsection 53(1) provides similarly but in relation to those events occurring after the end of the maximum interim period. This recognises that the maximum interim period may be different depending on the time that has elapsed since the change of care day, and the nature of the care arrangement. New subsection 53(1) also takes the maximum interim period into account, so that section 51 does not apply in cases where the Registrar has revoked a determination of a responsible person's percentage of care for the child, under section 54F or 54H. New subsection 53(2) further provides that section 51 does not apply in relation to a responsible person in relation to whom a determination has been made under section 49 or 50, if an earlier determination determined the responsible person's percentage of care for the purposes of subsections 51(3) and 51(4), the later determination is made after the end of the maximum interim period for the determination, and the later determination relates to the same care arrangement as the earlier determination. 55. The Revised Explanatory Memorandum does not expressly address how paragraph 53(1)(c) is to be construed. However, as stated in the bolded paragraph in the above extract, the Revised Explanatory Memorandum indicates that for the purposes of paragraph 53(1)(c), the exercise of either section 54F or section 54H is that occurring in the context of the maximum interim period. Further, the Revised Explanatory Memorandum confirms the purpose of section 51, and the importance of its place in ensuring that care arrangements are complied with and the intention of extending, rather than limiting, the application of interim periods. This is consistent with the Tribunal's earlier observations that the interpretation now being contended by the Child Support Registrar does not appear consistent with the scheme of the legislation in relation to care, and in particular in relation to the stated intention of extending the application of interim care periods. Of further note, the Revised Explanatory Memorandum suggests that the new subsection 53(1) was intended to replicate the old section 53, but taking into account the new concept of a 'maximum interim period' rather than the previous effective maximum interim period of 14 weeks that was in place prior to the 2018 amendments. If the amendments to section 53 in 2018 had been intended to preclude the operation of section 51 in any circumstance in which a pre-existing percentage of care determination was revoked under section 54F or section 54H, that would have been a significant change to the operation of the legislation, effectively almost rendering section 51 null and void. The Revised Explanatory Memorandum does not reveal any such intention. 56. The Tribunal also considered the interpretation of this Tribunal differently constituted on first review in considering a similar factual position (that is, where pre-existing percentage of care determinations were required to be revoked under section 54F and the change in care was notified after expiry of the maximum interim period) in Castle and Jonas (Child support) [2022] AATA 1702 (Castle and Jonas). In that decision the Tribunal 'read in' words to paragraph 53(1)(c) so that it read 'the Registrar has revoked the determination under section 54F or 54H after the end of the maximum interim period for the determination. As recognised in Castle and Jonas, in Taylor v The Owners - Strata Plan No 11564 (2014) 253 CLR 531 (Taylor), the High Court stated that: The question whether the court is justified in reading a statutory provision as if it contained additional words or omitted words involves a judgment of matters, of degree. That judgment is readily answered in favour of addition or omission in the case of simple, grammatical, drafting errors which if uncorrected would defeat the object of the provision. It is answered against a construction that fills "gaps disclosed in legislation" or makes an insertion which is "too big, or too much at variance with the language in fact used by the legislature". 57. In Castle and Jonas, the decision to 'read in' the additional words was reached on the basis that to do so would avoid the manifestly absurd result that there would otherwise be 'no scope, or almost no scope, to ever make interim determinations once a child support case has commenced' as paragraph 53(1)(c) would prevent interim periods applying pursuant to section 51 if the pre-existing determinations had been revoked pursuant to section 54F or 54H. Further, in Castle and Jonas it was stated that 'reading in' the additional words would give effect to the 'legislative intent as expressed in the Explanatory Memorandum and as can be discerned from a broader reading of the provisions that deal with the making of care decisions', that is 'if an interim determination could have been made or was made in respect of the relevant care arrangement but the maximum interim period would have ended or has ended, then section 51 does not apply in respect of the care decision that is currently being made.' 58. The Tribunal acknowledges the approach in Castle and Jonas but, with respect, considers the 'reading in' of the words 'after the end of the maximum interim period for the determination' goes beyond what is contemplated by the High Court in Taylor of a case of 'simple, grammatical, drafting errors which if uncorrected would defeat the object of the provision'. 59. Further, for the reasons that follow, the Tribunal does not consider that there would be 'no scope, or almost no scope, to ever make interim determinations once a child support case has commenced'. 60. The Tribunal notes that the Guide, whilst containing general guidance in relation to various aspects of the interim care provisions, provides no guidance in relation to this particular issue. 61. Having regard to all of the above matters, the Tribunal considered the actual wording of the whole of paragraph 53(1)(c), noting in particular the use of the word 'determination' within the subsection (emphasised by the Tribunal in bold underline) as follows: (1) Section 51 does not apply in relation to a responsible person in relation to whom a determination is to be or has been made under section 49 or 50 if: (a) in a case where subparagraph 49(1)(a)(i) or 50(1)(a)(i) applies in relation to the determination-the day the application referred to in that subparagraph is made is after the end of the maximum interim period for the determination; or (b) in a case where subparagraph 49(1)(a)(ii) or 50(1)(a)(ii) applies in relation to the determination-the day referred to in that subparagraph is after the end of the maximum interim period for the determination: or (c) the Registrar has revoked the determination under section 54F or 54H. 62. There are a number of 'determinations' to which the references to 'determination' in section 53 could apply. 63. Section 53 follows on immediately from section 51. If the requirements of section 51 are met, subsections 49(2) and 50(3) do not apply and, subject to subsection 51(5), subsection 51(2) requires a determination of two percentages of care for the relevant person. Section 53 then immediately follows on in the Act to state that section 51 does not apply in relation to a determination that is to be or has been made if paragraphs 53(1)(a), 53(1)(b) or 53(1)(c) apply. Paragraphs 53(1)(a) and 53(1)(b) relate to initial child support applications and situations where a relevant dependent child is added to a child support case and do not arise for consideration in relation to this application. 64. Child Support's now position is that where a percentage of care determination is revoked under section 54F in any circumstances, section 51 cannot apply. However, as is suggested by the Revised Explanatory Memorandum where it states: Newsubsection 53(1) also takes the maximum interim period into account, so that section 51 does not apply in cases where the Registrar has revoked a determination of a responsible person's percentage of care for the child, under section 54F or 54H. the Tribunal's concludes that section 51 does not apply only in the restricted situation where revocation under section 54F occurs within a maximum interim period, with the Revised Explanatory Memorandum clarifying that the operation of paragraph 53(1)(c) is linked with the maximum interim period. 65. This position is consistent with and links with other relevant provisions of the legislation including, for example, subsection 53A(4) which provides that there is no interim period in respect of a percentage of care determination made under sections 49 or 50 before the end of the maximum interim period for another determination under those sections, with sections 54FA and 54HA prescribing for that scenario. Subsection 53A(4) relevantly states as follows: (4) A determination under section 49 or 50 of a responsible person's percentage of care for a child does not have an interim period if the determination is made under that section before the end of the maximum interim period for another determination under either of those sections of the responsible person's percentage of care for the child (see sections 54FA and 54HA). 66. This interpretation also explains the qualification in paragraph 54F(2)(a), triggering revocation under section 54F only when section 51 did not apply when previous determinations were revoked, section 51 did apply but the maximum interim period has ended or section 51 did apply, the interim period has finished however the maximum interim period has not ended and the earlier determination has been suspended under section 54FA. 67. The Tribunal's view therefore is that the determination to which section 53 refers in the introductory words of the section is the determination made after the revocation of the previous determination, that is the determination made pursuant to section 51. Section 53 follows on from section 51 and it is that immediately referred to section 51 determination to which paragraph 53(1)(c) applies, preventing the application of an interim period to that determination. That is, paragraph 53(1)(c) (only) prevents the application of a further interim period if a determination initially made under section 51 is revoked under section 54F or 54H within the maximum interim period. Section 51 does not apply only in the restricted situation where revocation under section 54F occurs within a maximum interim period. 68. The Tribunal considers this interpretation consistent with the clear intention of the 2018 amending legislation, introducing the central concept of the maximum interim period. Further, as already canvassed, the idea that such an obviously integral part of the scheme as interim periods would apply in only rare cases is nonsensical. This interpretation is also consistent with the emphasis shown in the Revised Explanatory Memorandum of the importance of recently established court-ordered and other care arrangements and the provision of incentives for persons with increased care taking reasonable action to participate in family dispute resolution. 69. Paragraph 53(1)( c) therefore does not prevent the operation of section 51 in the present case. 70. The Tribunal therefore concludes that section 51 can apply to the 6 February 2019 change in care (if the necessary requirements are met). The Tribunal observes that its conclusion is consistent with the Child Support Registrar's initial submissions of 13 June 2023 and Child Support's original decision in relation to the 6 February 2019 change in care. [emphasis in original - footnote references omitted] 36 The passage just excerpted highlights the disparate views within the Tribunal to which I have referred, as well as the text of the explanatory memorandum, which proved influential. 37 In terms of principle with respect to either "reading up" or "reading down" the text of a statute or, as is sometimes put, reading the text with the supply or omission of words, the pertinent modern authority at ultimate appellate level in Australia is Taylor v The Owners - Strata Plan No 11564 (2014) 253 CLR 531 (Taylor). One finds in the majority judgment in that case, at [35] to [40], a collection and discussion of pertinent earlier authority. 38 It was observed in the joint judgment, at [38]: The question whether the court is justified in reading a statutory provision as if it contained additional words or omitted words involves a judgment of matters of degree. That judgment is readily answered in favour of addition or omission in the case of simple, grammatical, drafting errors which if uncorrected would defeat the object of the provision. It is answered against a construction that fills "gaps disclosed in legislation" or makes an insertion which is "too big, or too much at variance with the language in fact used by the legislature". [footnote references omitted] 39 There then follows a reference to an influential speech by Lord Diplock in Jones v Wrotham Park Settled Estates [1980] AC 74, in respect of the reading of words into a statute referred to three necessary conditions for filling a gap, but it is only necessary in this case to refer to the third. Of the third, his Lordship stated , at 105 to 106: … possible to state with certainty what were the additional words that would have been inserted by the draftsman and approved by Parliament had their attention been drawn to the omission before the Bill passed into law. Unless this third condition is fulfilled any attempt by a court of justice to repair the omission in the Act cannot be justified as an exercise of its jurisdiction to determine what is the meaning of a written law which Parliament has passed. Such an attempt crosses the boundary between construction and legislation. It becomes a usurpation of a function which under the constitution of this country is vested in the legislature to the exclusion of the courts. 40 That third condition, as so stated, was later reformulated by Lord Nicholls of Birkenhead's in Inco Europe Limited v First Choice Distribution [2000] 1 WLR 586, at 592. As was noted in Taylor, at [39], fn 84, the reformulation was that, the Court must be absolutely sure of the substance, although not necessarily the precise words, the legislature would have enacted. 41 Of Lord Diplock's conditions, including the third, it was observed in the joint judgment in Taylor that they accorded with the statements of principle in an earlier High Court case, namely Cooper Brookes (Wollongong) v Commissioner of Taxation (1981) 147 CLR 297. 42 It was also observed in the majority judgment in Taylor, at [40]: In Inco Europe, Lord Nicholls of Birkenhead observed that even when Lord Diplock's conditions are met, the Court may be inhibited from interpreting a provision in accordance with what it is satisfied was the underlying intention of Parliament: the alteration to the language of the provision in such a case may be "too far-reaching". In Australian law the inhibition on the adoption of a purposive construction that departs too far from the statutory text has an added dimension because too great a departure may violate the separation of powers in the Constitution. 43 Similar sentiments had earlier been voiced in this Court by Pincus J, in Gauntlett v Repatriation Commission (1991) 32 FCR 73 (Gauntlett), at 77, in a passage later cited with approval by the Full Court in Ralph v Repatriation Commission (2016) 248 FCR 438, at [56]: … [t]his is not the first time in which the respondent Commission has implied in argument that provisions of this sort could not possibly have been intended to produce such anomalies as, literally read, seem to follow from them; but it is the Constitutional function of Parliament, and not that of the judges, to correct any anomalies thought to arise from applying the plain language of legislation. 44 Looking to the text of s 53(1) of the Assessment Act, it is clear enough that, of the three alternative circumstances that subsection specifies as circumstances in which s 51 does not apply, two of those alternative circumstances - namely, those specified in s 53(1)(a) and s 53(1)(b) - have an "after the end of the maximum interim period for the determination" qualification. There is no such qualification in the further circumstance as specified in s 53(1)(c). 45 However, regard to each of s 54F and s 54H discloses that one of the criteria which govern whether either the Registrar must (s 54F) or may (s 54H) revoke a determination is, when one reads s 54F(1)(d) or, as the case may be, s 54H(1)(d), in conjunction with subs (2) of those respective sections, a criterion as found in paragraph 2(b) a criterion that s 51 did apply in relation to the responsible person, but the maximum interim period for the determination has ended. 46 Thus, by this process, a sentiment of the "end of the maximum interim period", apparent on the face of s 53(1)(a) and s 53(1)(b) can be seen to be, in certain circumstances, also a criterion which can inform an application of s 53(1)(c). Even so, it may very well be that there is, having regard to the text, a gap in s 53(1)(c), as read even in that context. And that gap may be that described by the Tribunal in its reasons. But the Tribunal's reasons, and those of the Tribunal in earlier decisions - namely, Castle and Jonas (Child support) [2022] AATA 1702 and Mendez and Morton (Child support) [2019] AATA 3844 - show that there is no ready answer as to precisely what words need to be supplied to address any such gap. Truly, there is no certainty of the kind referred to in Taylor or Lord Nicholls of Birkenhead's, third criterion, as reformulated and approved in Taylor, as to what language needs to be supplied to address any gap of the kind apprehended by the Tribunal as a result of the amendment made to s 53. 47 It is not permissible to substitute the text of an explanatory memorandum for the text approved by Parliament. Section 15AA of the Acts Interpretation Act 1901 (Cth) does permit recourse to an explanatory memorandum to assist in constructional choices, but it is not a license for substituting the text of an explanatory memorandum for the text of an Act of Parliament. To do so would, as Pincus J observed in Gauntlett, exceed the constitutional function of judges. 48 Any change to s 53 thought necessary as a result of the exposure of a gap by the Tribunal's reasons and those of this Court, it is a matter for the parliamentary, not the judicial, branch. On the facts of the present case, there were relevant determinations which engaged, on their face, s 53(1)(c). The criterion specified in that paragraph, in turn, that had the effect of rendering s 51 of the Assessment Act inapplicable. In turn, that means that the grounds of appeal must be upheld, such that the Tribunal was an error in looking, in the circumstances of the present case, to s 51 of the Assessment Act. 49 The appeal must therefore be allowed. The Tribunal decision must be set aside, and the proceeding remitted to the Tribunal for further review, according to law. 50 I note that the Registrar does not seek an order for costs. That, of course, is an administrative value judgement, but, with respect, it certainly accords with the justice of this case, and the particular difficulties of construction presented by the Assessment Act. These are unfortunate, given the systemic importance of that Act to so many Australians. 51 I record my appreciation in respect of the assistance provided to the Court by Mr McLeod KC and Mr Maynard of counsel, who appeared for the Registrar. I certify that the preceding fifty-one (51) numbered paragraphs are a true copy of the Reasons for Judgment of the Honourable Justice Logan.