1. The issues that arise in this application:
   • Should the existing care percentage determination be revoked and if so, from what date should the revocation take effect?
   • In determining to revoke the existing care determination, what is the relevant care period in which to assess the care arrangements of the children and what are the percentages of care for the children during the care period?
   • In revoking the existing care percentage determination, what new care determination should be made?

1. In considering this application, I have outlined the evidence of the parties below and my assessment of this evidence before the consideration of the relevant legislative provisions.

1. Ms JMGW summarised her position in relation to this application, with reference to her written submissions. Ms JMGW confirmed in her oral evidence that there had been court orders made in relation to the care of the children in November 2012 and there were minor variations of the care. As an example of the modification of the care, she stated that the court orders originally prescribed that the father would have care of the children on a Wednesday night but that this stopped in 2014, however, it did not alter the care with Ms JMGW having 67% care of the children and Mr ZSRQ having 33% care of the children.
2. She stated that the catalyst for the care change from 1 January 2023 was for study and mental health reasons, as both children have generalised anxiety, with the younger child also exhibiting undiagnosed autism spectrum traits. In December 2022 the youngest child was also diagnosed with type I diabetes. In December 2022 while on holiday with the father, a dispute arose and the girls were returned early to her care. On 2 January 2023, she stated that Mr ZSRQ stated by phone that the children should decide as to when he would have care and then would make arrangements for their transportation.
3. Ms JMGW stated that this started an ad hoc arrangement with the children deciding when and how long they would spend time with him. She stated that she did not have communication with the father and that the children would inform her when they would be seeing the father. Mr ZSRQ would make transport arrangement for the care of the children. As a result, there was a marked reduction in overnight care and regular day time contact with Mr ZSRQ. Ms JMGW stated that because nights can only be counted retrospectively in this arrangement, it only became clear at the end of 2023.
4. Ms JMGW stated that there was no set schedule as to when the care took place, and there was no set pattern to the care. She stated that the care would occur when the children decided. She stated that in her original contact, she made an error in the date and told the Registrar's delegate that the care changed on 1 January 2022 but she later corrected the date on 6 May 2024,[2] prior to the objection decision being made. She stated that she would complete the calendar on the morning of the day after for the previous day depending on where they were for that day. Ms JMGW stated that the calendar was in the kitchen and completed the day after because there were times that the children organised to spend time with their father and there was a least two occasions where she was called late in the evening to collect them because they wanted to spend the night at her home instead. She sometimes encouraged them, particularly when there was a birthday, but that was the extent of her involvement in determining the care arrangements. Ms JMGW stated that she completed the calendar[3] throughout the period.
5. The contact on 6 May 2024 was discussed with Ms JMGW. The record of the conversation indicates that Ms JMGW was asked about why he stated that the care changed on 2 January 2022 and Ms JMGW is recorded as stating that there was a verbal conversation between the parents and this was the date the care changed. Ms JMGW was asked during the conversation to provide evidence and she stated during the conversation that she only had calendar evidence from 2023 and therefore the date of the change would need to be changed to 1 January 2023. In her evidence at hearing, Ms JMGW clarified that during the conversation she realised the error of the date she submitted and that the conversation took place after the youngest child's diabetes diagnosis in December 2022 and that is how she knows that the change in care started in January 2023 and not in 2022.
6. Ms JMGW stated that the father's care of the eldest child was around 37 nights according to her calendar records for 2023, and around 35 nights for the younger child in 2023. She stated that she could not recall having the option of providing evidence when first notifying of the change in care. She could not recall being asked to provide evidence.[4] Ms JMGW confirmed that she received letters from the Registrar electronically through her MyGov account. Ms JMGW stated she did not recall receiving or reading a letter requesting evidence of the change in care from the Registrar after her notification.[5] Consequently, she didn't provide any evidence of the care change.
7. Ms JMGW stated that at the time she was dealing with unprecedented demands, in particular in relation to the youngest child and her diagnosis at the time of type I diabetes and coming to terms with and learning to manage this condition. In addition, Ms JMGW stated that the child was undiagnosed with autism and suffering significant breakdowns on a regular basis, and so her time was taken up with managing these issues and the household as well as working full-time. This was also the reason why she didn't apply earlier for the change in care but also because of the unpredictability nature of the arrangement because there is no set schedule for the care that Mr ZSRQ had with the children.
8. In addition to the oral evidence, Ms JMGW provided written submissions consistent with her oral evidence. In the written submissions, Ms JMGW outlined in more detail the arrangements for the care of the children from January 2023 were discussed between herself and Mr ZSRQ. Ms JMGW states in these submissions that she made a written record of the conversation. Ms JMGW states that the conversation outlined that the children would make the decision on when and how they would spend time with the father; rather than a pre-set routine and Mr ZSRQ would make arrangements for their transport; the arrangement was random; at times the children would spend time together with Mr ZSRQ and other times individually. Ms JMGW acknowledges in her written submissions that on reviewing the calendar that the care on 17 November 2023 was not accounted for in her records. Ms JMGW further submits that notwithstanding that missed night, her records are more accurate than not. In addition to her statements as to what care was occurring, Ms JMGW submitted a statement from the eldest child's psychologist, which states that the child reported that she had spent fewer than 40 nights in the father's care in 2023, having not been in his care for January and February 2023, and that her time with the father was sporadic and inconsistent. A further letter from a third party who was assisting with the younger child's behavioural concerns, also refers to being made aware by the child of a reduction in the time that they are spending with the father. Ms JMGW also provided the delegate of the Registrar a statement from her husband which corroborates the calendar records provided by Ms JMGW.

1. Mr ZSRQ stated initially at the hearing that he had given all of his evidence in these proceedings and was unsure as to what more he could add. Mr ZSRQ stated that Ms JMGW's evidence that they agreed to a change the care of the children, but this did not occur in January 2022. Mr ZSRQ had asked for the care to be altered from 2022, so that his care could align with his then partner's care of her own children, but Ms JMGW refused to change the arrangement and said that they would stick to the court orders. This occurred in late 2021. Mr ZSRQ further stated that it was not a mistake that Ms JMGW notified of a change in care from 2 January 2022 and that it was only when he produced this information that there was a correction by Ms JMGW of the date from which the care changed.
2. Mr ZSRQ stated that the Registrar's delegate made the change without consultation, even though the notes indicate he was contacted about the change in care when notified. Mr ZSRQ stated that he was not notified of the change. He stated that he objected to the care change because there had been no agreement and there had not been a change. Mr ZSRQ stated that he didn't take any notes or keep any calendars of the care. Mr ZSRQ questioned the veracity of the document as there were dates marked on the calendar where the children were in his care.
3. He stated that the eldest child had a boyfriend who lived near his home and so subsequently she spent most weekends with him in 2023. There was a period in January 2023 that he didn't see the children, he couldn't recall how long that was for - it might have been for a few weeks but was not sure. Mr ZSRQ stated that the care of the younger child resumed to be in line with what was occurring before the period in January 2023 when they did not spend time with him. He stated that there was never a conversation regarding the care being left to the children to decide. In December 2023 the children travelled overseas for 4 weeks with Ms JMGW and then the eldest child stayed with him for four weeks in January 2024 when she returned.
4. Mr ZSRQ confirmed that the care according to the court orders was every Wednesday and then every second weekend and half the school holidays. He confirmed that the Wednesday care stopped in 2014 and the children remained in his care for longer on the Sunday. Mr ZSRQ stated that there were a few weeks where the youngest child did not come into his care but it wasn't a change in the pattern of care.
5. Mr ZSRQ provided written statements to the delegate of the Registrar when he lodged the objection, which were consistent with his statements at hearing. Included in the information provided on objection is evidence that he had care of the children on dates not recorded on Ms JMGW's calendar, specifically on 12 August 2023 and 17 November 2023. Mr ZSRQ provided a statement from his sister in support of his assertions that there has been no change in his care of the children.

Assessing the evidence as to the pattern of care for the children

1. In considering the evidence before it, I am required to reach conclusions based on 'rationally probative evidence' rather than mere 'suspicion or speculation'.[6] The evidence produced by the parties 'is to be weighed according to the proof which it was in the power of one side to have produced, and in the power of the other to have contradicted'.[7]
2. Weighing the evidence using those principles, I am not satisfied that Ms JMGW has evidence that the children's care changed from 1 January 2022 but that there is evidence of a change in the care from 2 January 2023. I am satisfied that the calendar of the care for 2023 provided by Ms JMGW shows the care that was occurring from 2 January 2023. I accept Mr ZSRQ's evidence indicates that there were at least two dates where he had care of the children which are not included in the calendar. While accepting Mr ZSRQ had the care of the children on these dates, and I note that Ms JMGW has acknowledged that she did not include at least one of these dates, it is does not lead me to conclude that the remainder of the calendar should not be accepted.
3. In terms of other dates indicated on the calendar, Mr ZSRQ's evidence as to not having the care of the children in December 2023 while overseas and that he had the care of the eldest child for January 2024 is accurately reflected in the calendar.
4. In addition to the calendar provided, I have also considered the statements of the eldest child's psychologist and the letter from the consultant assisting with the youngest child's behavioural issues. Both statements, while reliant on information provided to them by the children, corroborate in general terms that Ms JMGW's care increased in 2023 and the amount of the care as per the calendar provided.
5. Mr ZSRQ has stated that the care of the children did not change, however he has not maintained records. He has explained the reason for this, as it was not in issue during the period and he has not had a need for such records. Mr ZSRQ's written submissions to the delegate refer to the care from January 2024 and the nights in care in March and April 2024. His statement is that the care did not change in 2023. Mr ZSRQ states that no conversation regarding the care of the children occurred in January 2023 where it was agreed that the children would determine when they would be in his care. He states that a conversation about amending the pattern of care occurred in 2021, initiated by him, to which Ms JMGW declined and asked to stick to the court orders. The statement provided to the delegate from his sister refers to her seeing the children in his care and his payment of costs for the children, including medical costs.
6. The evidence relating to the care from January 2023 was not provided until after the phone call to Ms JMGW on 6 May 2024 with a delegate of the Registrar. The conversation indicates that Ms JMGW confirmed that she did not have a calendar prior to 2023 and that the actual care from 2 January 2023 be considered. Prior to this discussion, no evidence apart from her notification of the care change, was provided.
7. Ms JMGW stated she could not recall being asked for evidence prior. She could not recall the letters sent to her at the time she notified of the change in care on 7 January 2024. She stated that the issues regarding the youngest child's diagnosis of type I diabetes and learning to manage this condition and that the child was undiagnosed with autism and suffering significant breakdowns on a regular basis meant she was not aware of the request for the information. She explained at hearing that during the conversation she realised the error of the date she submitted.
8. I accept that the care of the children has changed from 2 January 2023. While I note that Ms JMGW omitted to include some days where the children were in the father's care, it does not mean that I must reject the other evidence of the change in the care of the children. In particular, the evidence of the psychologist and consultant indicate that the care of the children had increased for the mother and decreased for the father. I am persuaded, based on the evidence before me, that there has been a change in the care of the children from 2 January 2023. I therefore find there is a basis to revoke the existing care percentage determination.

Should the existing care percentage determination be revoked and if so, from what date should the revocation take effect?

1. The law that applies in this case is the Child Support (Assessment) Act 1989 (the Assessment Act) and the Child Support (Registration and Collection) Act 1988 (the Collection Act). The percentage of care used in a child support assessment assist in determining the applicable percentages of the cost of the child or children that each parent is meeting directly through the care they provide. A parent or non-parent carer's percentage of care is calculated based on the care they provide, or are likely to provide, for the child in the relevant care period. In conducting the review, I may have regard to the Child Support Guide (the Guide) where relevant. However, I am not bound to follow it.[8]
2. If notified of an alleged change in the actual or anticipated pattern of care of a children, the Registrar must consider whether such a change occurred. If satisfied of a change, then the percentages of care used in the assessment may, or in some cases must, be revoked (sections 54F, 54G and 54H of the Child Support (Assessment) Act 1989 (the Assessment Act) and another assessment must be made using newly determined percentages of the actual care the parties provided or are likely to provide to the children in a newly determined care period.[9]
3. In this matter, I am satisfied that the relevant provision under which care must be revoked is section 54F of the Assessment Act. In determining section 54F of the Assessment Act applies, I find that requirements to revoke under section 54G of the Assessment Act are not met, as Ms JMGW did not notify the Registrar 'of the matter referred to in paragraph (b) of this subsection within a period that the Registrar considers is reasonable in the circumstances.' It is not disputed that Ms JMGW notified the Registrar of the changed care of the children on 7 January 2024. Ms JMGW stated that she was not able to notify sooner, as the care of Mr ZSRQ was not according to a set pattern of care and therefore it could not be discerned until after the care had occurred. Ordinarily, a change in care is required to be notified within 28 days of it occurring.[10] Notification here was made some 12 months after the change occurred. I am not satisfied that the explanation for the delay was reasonable in the circumstances and accordingly, as paragraph 54G(1)(d) is not met, section 54G does not apply and the existing percentages of care are not able to be revoked pursuant to this section.
4. In considering changes, the Registrar usually considers a care period of 12 months from when the actual pattern of care of a children began or changed.[11] If the assessment is made before the end of the care period, the Registrar must make a partially forward-looking judgment as to the care of the children a party to the assessment is likely to provide over the period. In doing so, the Registrar considers whether a party to the assessment has had, or is likely to have, a 'pattern of care' for the children during the care period. The pattern of care informs the assessment of the 'percentage of care' to be used.
5. The pattern and percentage of care will commonly be determined by reference to the number of nights each children spends in the care of each party to the assessment.[12] This is usually the best method of determining the care of each party to the assessment. However, there may be occasions where the nights in care does not accurately reflect care arrangements for the children and other factors will need to be considered.[13]
6. Once it has been determined that the pattern of care for children has changed and that the existing care determination should be revoked, a new care percentage determination will be made based on the actual pattern of care that a person has had or is likely to have.
7. The Registrar submits that original decision in this matter was a 'care percentage decision' as defined under section 4 of the Collection Act, as it was 'a decision as to the particulars of an administrative assessment, to the extent that the decision involves a determination under Subdivision B of Division 4 of Part 5 of the Assessment Act' as held in Child Support Registrar v MQMV [2019] FCA 1171 (MQMV). I agree with this proposition as submitted by the Registrar and stated by Flick J in MQMV.
8. In addition, the Registrar submitted that I am limited to reviewing a decision that had already been made. In Re Drake v Minister For Immigration And Ethnic Affairs (1979) 2 ALD 60 Bowen CJ and Deane J stated as follows in relation to the review of decisions by the AAT:

In its review of an administrative decision, it is subject to the general constraints to which the administrative officer whose decision is under review was subject, namely, that the relevant power must not be exercised for a purpose other than that for which it exists (citation omitted), that regard must be had to the relevant considerations, and that matters "absolutely apart from the matters which by law ought to be taken into consideration" must be ignored. (citations omitted).[14]

1. The Registrar further submitted that the decision before me is also confined to answering the same question, as stated by Finn J in Comcare v Burton [1998] FCA 1144; (1989) 157 ALR 522 '...to answer the same question(s) as was (were) before the reconsideration decision-maker.' [15] That question, according to the Registrar's submissions, was to consider, on AAT first review (and subsequently in this review), the objection to the original decision, which found that the care of the children changed on 2 January 2022 and decide whether to allow or disallow that decision in whole or in part. The Registrar submits that the objection officer was required, and the ART on review, to consider whether there had been a change in care of the children as notified by the applicant. The Registrar submitted that, as stated by the High Court in Shi v Migration Agents Registration Authority [2008] HCA 31 that the review must redo what was done:

100. The AAT Act provides for the review of decisions by a body, the Tribunal, that is given all of the powers and discretions that are conferred on the original decision-maker. As Brennan J rightly pointed out in an early decision of the Tribunal (citation omitted), not all of the powers that the Tribunal may exercise draw upon the grant of powers and discretions to the primary decision-maker:

"A decision by the Tribunal pursuant to s 43(1)(a) to affirm the original decision leaves the original decision intact, and that is the only decision which takes effect under the enactment: the original powers are not drawn upon by the Tribunal's order. Equally, a decision to set aside the decision under review and remit the matter for reconsideration pursuant to s 43(1)(c)(ii) requires the original repository of the powers and discretions to exercise them afresh: they are not exercised by the Tribunal. Section 43(1) grants the original powers and discretions to the Tribunal, but it does not require the Tribunal to exercise them unless the Tribunal is making a fresh order the effectiveness of which depends upon their exercise."

But subject to that qualification, the Tribunal's task is "to do over again" what the original decision-maker did (citations omitted).[16]

1. In redoing what was done, the Registrar submits that subsequent information provided by the parents during the course of the objection process regarding the care of the children provided in 2023 and 2024 would have been to embark on a course of fresh decision-making rather than the consideration and determination of the objection to the decision already made in respect of the claimed change in January 2022.
2. Relevantly to the circumstances to the matter before me,[17] section 50 of the Assessment Act requires that the Registrar is satisfied as follows:

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

1. As observed in Child Support Registrar v BKCZ [2023] FCA 1109 (BKCZ):

Generally, the intention of the Parliament must be discerned by the language used in the statute and, in terms of the language used, the words should be given their natural and ordinary meaning (Project Blue Sky Inc v Australian Broadcasting Authority (1998) 194 CLR 355; [1998] HCA 28 (per Brennan CJ, McHugh, Gummow, Kirby and Hayne JJ)).[18]

1. The Court in BKCZ rejected what was described as the 'point in time' approach, which has been submitted by the Registrar in this application. While BKCZ refers to the 'point in time' approach as it relates to the provision of further evidence of the change in care supporting a finding of fact regarding the change, in my view the principle equally applies in allowing a decision maker, on review, to make a different finding of fact of when the care changed based on the evidence before them. As stated in BKCZ:
   1. There is nothing contained in the statutory text that clearly expresses a statutory indication as to a temporal element. The words are in broad terms, allowing flexibility for the decision-maker. There is no use of words which refer to any earlier date which might limit the information which might be considered to an earlier point-in-time than the date upon which the matter comes before the decision-maker (either the Registrar or the AAT standing in the shoes of the Registrar).
   2. The words are sufficiently flexible to enable a decision-maker to take into account what the responsible person has had and what the person is likely to have, depending upon the time in the care period that the decision is taken.
   3. Without doubt, the most reliable information which will assist in undertaking the task outlined in ss 49 and 50 is information which is based upon actuals, rather than what might be likely. As Mason J said in Peko-Wallsend at 45(also referred to at [33] above):

It would be a strange result indeed to hold that the [decision-maker] is entitled to ignore material of which [the decision-maker] has actual or constructive knowledge and which may have a direct bearing on the justice of making the [decision], and to proceed instead on the basis of material that may be incomplete, inaccurate or misleading.

1. The sections themselves point to a consideration of "actual care". For example, s 50(3) requires that the percentage of care determined "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" (italics added).
2. The section points to the objective of determining the "actual care". Those words used are directory in nature in that the subsection requires that the percentage "must" be a percentage that corresponds with the actual care. The section goes on to allow the decision-maker flexibility to cater for different times during the care period that a decision is being made by referring to the Registrar being satisfied by reference to what the responsible person "has had, or is likely to have". The most effective way of determining the "actual" care is to consider what has happened if that information is available.
3. The delineation, rather than being by reference to when the Department is notified, is up to the date the actual information is available. So, in terms of the requirement (and adopting the description outlined in [64]), the delineation would be:

(a) on the one hand, the assessment would be from the date of the change to when the decision-maker considers the matter, so as to give effect to the phrase "has had"; and

(b) on the other hand, so as to give effect to "is likely to have", a prospective assessment of the balance of the care period (when actual figures are not available) informed by the actual figures which are available.

1. Such an approach better fulfils the object of determining "actual care" and so is more consistent with the requirements set out in ss 49 and 50.
2. The consideration in this context of the wording of section 54F(1)(a) of the Assessment Act, as is relevant in this matter, where care must be revoked if '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 (emphasis added)' also points to the consideration of the 'actual care' occurring as to the basis on which the care should be revoked.
3. The events from 1 January 2023 have indeed occurred after the date stated to the Registrar by Ms JMGW, but nonetheless inform on the pattern of care during the care period pertaining to the change notified. The application of BKZC to the circumstances of Ms JMGW and Mr ZSRQ's matter is in my view, that Ms JMGW's evidence in these proceedings is of a pattern of care notified on 7 January 2024 which in fact had occurred (as a matter of historical fact) during the care period from 1 January 2023.
4. I am satisfied that the percentages of care should be assessed as 9% to Mr ZSRQ and 91% to Ms JMGW from 2 January 2023. I have based this conclusion and preferred the evidence of the care as provided by Ms JMGW for the care period. While I note that there were some days in which Mr ZSRQ had care which were not included in MS JMGW's calendar, I am satisfied that of the overall pattern of care as provided was in accordance with the calendar. I find that the evidence as provided establishes this pattern of care. Accordingly, the previous determination of care made on 8 January 2013 is revoked. I am satisfied that Ms JMGW notified of the care change on 7 January 2024. As the Registrar was not notified of the change in care within 28 days of the care change, the existing care determination is revoked from 6 January 2024 and a new care determination takes effect on the date the care was notified on 7 January 2024 (as per subparagraph 54F(3)(b)(i) of the Act) for Ms JMGW. For Mr ZSRQ, whose care has decreased, the existing care determination is revoked from 1 January 2023 and a new care determination takes effect from the change of care day, that is 2 January 2023 (subparagraph 54F(3)(b)(ii) of the Act).

1. The Tribunal sets aside the decision under review and remits the matter for reconsideration in accordance with the order that:

• The existing percentage of care determination of 67% for both children to Ms JMGW is revoked from 6 January 2024 and a percentage of care determination of 91% applies for both children to Ms JMGW from 7 January 2024; and

• The existing percentage of care determination of 33% for both children to Mr ZSRQ is revoked from 1 January 2023 and a percentage of care determination of 9% applies for both children to Mr ZSRQ from 2 January 2023.

[1] Administrative Review Tribunal (Consequential and Transitional Provisions No.1) Act 2024.

[6] Minister for Immigration and Ethnic Affairs v Pochi [1980] FCA 85; (1980) 31 ALR 666 at 685.

[7] Coshott v Prentice [2014] FCAFC 88; (2014) 221 FCR 450 at [80], quoting Blatch v Archer [1774] EngR 2; (1774) 1 Cowp 63 at 65; [1774] EngR 2; 98 ER 969 at 970.

[8] Re Drake and Minister for Immigration and Ethnic Affairs (No 2) (1979) 2 ALD 634; G v Minister for Immigration and Border Protection [2018] FCA 1229.

[9] Subsection 49(2) and paragraph 50(1)(b) of the Assessment Act.

[11] subparagraph 50(1)(b)(ii) of the Act and section 2.2.1 of the Guide.

[12] Section 54A of the Assessment Act and section 2.2.1 of the Guide.

[13] Polec & Staker & Anor (SSAT Appeal) [2011] FMCAfam 959.

[14] (1979) 2 ALD 60 at 69.

[15] Comcare v Burton [1998] FCA 1144; (1998) 157 ALR 522 at 528.

[16] Shi v Migration Agents Registration Authority [2008] HCA 31 at [100].

[17] Without reproducing the section 49 in its entirety, the consideration under section 49 of the Assessment Act applies only in circumstances where a responsible person has had, or is likely to have, no pattern of care. As both parents have had at least some care (that is, more than 0% care) at all material times, section 49 will not apply.