"[43] Hence, it was argued that if Ms Fletcher had been entitled to her debt against the defendant before proceedings were brought by the defendant against her and the plaintiff, then, as the proceedings brought by the defendant against her and the plaintiff were for a joint and several obligation, the debt owed by Ms Fletcher to the plaintiff could have been set off against the debt for which the defendant obtained judgment against both of them. It was submitted that the availability of the set-off should not depend upon the accident that judgment had already been obtained. To the contrary, so it was argued, the plaintiff should be entitled to set off against the judgment owed by it the amount owed by the defendant to Ms Fletcher where she was also jointly and severally liable on the same judgment debt as the plaintiff, in order to avoid circuity of action. Counsel submitted that if the plaintiff paid the whole of the judgment debt pursuant to the defendant's demand, it would be entitled to recover contribution from Ms Fletcher for half of the judgment debt paid, but she could recover $11,000 from the defendant. The same result is reached if the plaintiff, availing itself of the set-off available to Ms Fletcher, paid the defendant the difference between the two judgments, and if Ms Fletcher was given the benefit of the set-off on the claim for contribution.
[44] However, this submission demonstrates the reason why one joint and several obligor who is sued alone cannot raise a set-off to which his or her co-obligor is entitled ( Bowyer v Pawson (1881) 6 QBD 540). The reason is that, in a suit so constituted, rights of contribution between the co-obligors cannot be resolved. To take the present case, if the plaintiff were obliged to indemnify Ms Fletcher against her liability under the judgment in favour of the defendant, it would be unjust to allow the plaintiff to rely upon the set-off available to her against the defendant. If that were permitted, she would have to look to the plaintiff, rather than to the defendant, to recover the $11,000 owed to her by the defendant. There is no equity in allowing the plaintiff to distort the true position by taking advantage of a set-off available to her ( Lord v Direct Acceptance Corporation Ltd (in liq) (1993) 32 NSWLR 362 at 369). The position would be different if the co-obligors are both joined in a suit so that a set-off available to one is actually given effect to, and rights of contribution between them can be determined. In the absence of such a suit, the plaintiff is not entitled to avail itself of the set-off available to its co-obligor ( Bowyer v Patterson ).
[45] It is true that in Goodwin v Duggan , Handley and Beazley JJA said that it was possible that if the trustee had been sued alone, she could not have relied on a set-off available only to her co-trustee, rather than categorically stating that position. However, as a matter of principle and authority ( Bowyer v Pawson ), and conformably with the reasons of Powell JA in Goodwin v Duggan , in a suit so constituted, the trustee should not be entitled to raise the set-off available to her co-trustee.
[46] It follows that in an action to set aside the statutory demand, to which the only parties are the plaintiff and the defendant, and in which the set-off available to Ms Fletcher cannot be given effect to, nor rights of contribution between the plaintiff and Ms Fletcher determined, the plaintiff cannot avail itself of the set-off available to Ms Fletcher."
43 His Honour's decision was plainly not concerned with a guarantee and it may be for this reason that his Honour was not referred to the extensive case law which discusses the ability of a guarantor to raise an equitable set off which is available to the principal debtor against the creditor.
44 In New South Wales a convenient starting point for discussion of the guarantor case law is Cellulose Products Pty Ltd v Truda (1970) 92 WN (NSW) 561. After an extensive review of the authorities Isaacs J concluded as follows:
"This review of the cases lends no support to the submission that a surety when sued is entitled to set up in equity or at law as a equitable plea any cross action for unliquidated damages which the debtor may have against the creditor in respect of the transaction, the performance of which the guarantor had entered upon his guarantee; that is, in the absence of the debtor being before the court in the proceeding so as to be bound by verdict and judgments. This of course does not mean that the guarantor is without remedy; when he is sued he has a right immediately to join the debtor as a third party and claim complete indemnity from him. The debtor has then a right to join the plaintiff as a fourth party, claiming damages for breach of warranty and so obtain indemnity either in whole or in part. All the actions would be heard together, the rights of all persons determined and appropriate set-off's made after verdict, and if there be any surplus of damages over and above that which is required to meet the guarantee, the debtor will have recovered that from the creditor who, in the result, will get no more than that to which he would be justly entitled."