Slip Rule Overreach: Husband Wins Appeal After Court Turned Wife’s Personal Tax Debts Into Shared Liabilities

In Agar & Lemus [2026] FedCFamC1A 86, the Full Court allowed the husband’s appeal after final property orders were later amended under the slip rule in a way that substantially changed the parties’ obligations. The key error was that the primary judge used r 10.13 to amend orders so that the husband became exposed to the wife’s historical income tax liabilities dating back to 2004, even though the wife had not sought that order at trial and the husband had never agreed to share those liabilities. The Full Court held this was not a mere correction of an accidental slip — it was a controversial substantive amendment made without procedural fairness.

🧩 Facts and Issues

Facts:

The parties commenced cohabitation in 2003 or 2004, married in 2005, and separated in March 2020. Final property orders were made in May 2025, dividing the net property 60% to the wife and 40% to the husband.

A major issue was the wife’s unresolved tax position. She had not lodged income tax returns since at least 2004, despite the proceedings commencing in 2020 and the trial not occurring until February 2024. By the time judgment was delivered in May 2025, she still had not filed returns, meaning her income tax, CGT, penalties and interest had not crystallised.

The husband accepted that certain capital gains tax liabilities connected with property sales should be shared, but he opposed responsibility for the wife’s general income tax liabilities, penalties and interest. Later, both parties sought corrections to the final property orders under the slip rule. The primary judge amended the orders in a way that expanded the quarantined funds from specific CGT liabilities to all of the wife’s income tax liabilities from 30 June 2004, excluding penalties and interest.

Issues:

1. Could the Court use r 10.13 to amend final property orders so that the husband shared the wife’s historical income tax liabilities?
2. Was the amendment a genuine “slip” or a substantive change?
3. Was the husband denied procedural fairness because no party sought that order and he had not agreed to it?
4. Did the primary judge also err in amending the order dealing with sale/retention of the 1 P Street property?
5. What orders should the appellate court make to correct the error?

⚖️ Applicable Law – Legislation, Regulations, Rules

Federal Circuit and Family Court of Australia (Family Law) Rules 2021 (Cth)

• r 10.13 — slip rule / power to vary or correct orders in limited circumstances, including where an order does not reflect the Court’s intention or contains an accidental slip or omission.
• Sch 3 — costs schedule, used to fix the husband’s appeal costs.

Federal Circuit and Family Court of Australia Act 2021 (Cth)

• s 36(1)(b) — appellate power to make the order that should have been made.

📌 Precedents Relied On

The judgment did not turn on a detailed discussion of external authorities. The appeal was resolved by applying the limits of r 10.13, procedural fairness principles, and the appellate court’s power under s 36 to correct the orders.

🧠 IRAC Analysis

Issue

Did the primary judge exceed the permissible scope of the slip rule by amending final property orders to make the husband responsible for the wife’s unresolved historical income tax liabilities, where no such order was sought or agreed at trial?

Rule

The slip rule is not a vehicle for re-deciding a case, changing the substance of final orders, or introducing new controversial obligations after judgment. It can correct accidental slips, omissions, or orders that fail to reflect the Court’s actual intention.

However, where an amendment:

• creates a new substantive liability;
• is controversial;
• was not sought by either party;
• rests on an erroneous factual assumption; or
• is made without giving the affected party an opportunity to be heard,

then it is not a proper slip-rule correction. It becomes a procedural fairness problem and an appealable error.

Application

1. The tax amendment was not a slip — it changed the substance of the final orders

The original Order 24 dealt with quarantined funds for specific CGT liabilities connected with identified property sales. It did not make the husband responsible for the wife’s general income tax liabilities dating back to 2004.

The later amendment dramatically changed that. It expanded the order to cover all income tax liabilities of the wife from 30 June 2004, excluding interest and penalties. That was a major substantive change, not a clerical correction.

2. The amendment rested on an erroneous factual finding

The primary judge had stated in the original reasons that the parties agreed the wife’s unpaid tax liability should be taken into account and that both parties proposed a mechanism to quarantine money for her past income tax.

The Full Court held that this was wrong. The wife conceded on appeal that she had not sought an order requiring the husband to pay her income tax liabilities, and that the husband had not agreed to such an order. The husband had only agreed to share certain CGT liabilities, not the wife’s entire historical income tax burden.

3. The husband was denied procedural fairness

Because the wife had not sought the income-tax order at trial, the husband had no proper opportunity to argue against it. He had expressly opposed responsibility for the wife’s non-CGT taxation liabilities.

The Full Court held it was procedurally unfair to impose that liability later by way of slip-rule amendment. The amendment was “substantially controversial” and should not have been made under r 10.13.

4. Order 20(c) was also amended incorrectly

The appeal also concerned the order dealing with the 1 P Street property. Both parties had effectively adopted a common position about the correction needed. But the primary judge amended the order in a way that neither party sought and without giving them a chance to address that version.

The result was anomalous and inconsistent with other orders requiring the sale of the property and distribution of sale proceeds. The Full Court corrected the order by deleting the problematic words so the order aligned with the sale machinery.

Conclusion

The appeal was allowed. The Full Court:

• discharged the amendments that exposed the husband to the wife’s historical income tax liabilities;
• dismissed the wife’s Notice of Contention;
• corrected Order 20(c) using its appellate power under s 36(1)(b); and
• ordered the wife to pay the husband’s appeal costs fixed at $20,316.03.

🧠 Take-Home Lesson

This case is a strong warning about the limits of the slip rule. A court can correct accidental mistakes, but it cannot use r 10.13 to impose a new and controversial financial obligation after final property orders have been made.

The practical lesson is simple: CGT sharing is not the same as sharing all tax debt. If a party wants the other spouse to contribute to historical income tax liabilities, that relief must be clearly sought, argued, and supported by evidence at trial. It cannot be smuggled into the orders later as a “correction”.