For two decades, foreign groups entering Australia ran the same playbook: fund the local subsidiary with intercompany loans, centralise treasury offshore, and restructure once revenue justified it. That playbook broke on 1 July 2023. Australia’s rewritten thin capitalisation rules, enacted by the Treasury Laws Amendment (Making Multinationals Pay Their Fair Share, Integrity and Transparency) Act 2024, replaced the old asset-based debt tests with earnings-based limits for most entities.
For founders, CFOs, and tax leaders, the planning question has shifted from “Can we structure this?” to “Can we defend this if challenged?” This guide covers what US companies doing cross-border tax structuring for an Australian entity must know in 2026, starting with the Australian Taxation Office’s thin capitalisation rules.
What Are Australia’s Thin Capitalisation Rules?
Thin capitalisation rules limit the interest deductions of entities that invest or are controlled across the Australian border. They stop groups from stripping Australian profits through excessive related-party debt and the interest deductions it generates. The Australian Taxation Office (ATO) administers them as part of Australia’s alignment with the Organisation for Economic Co-operation and Development (OECD) Base Erosion and Profit Shifting (BEPS) project.
In short, these are interest limitation rules. They cap how much debt deduction a foreign-owned Australian entity can claim, regardless of how the interest rate itself is set.
What Changed in Australia’s Thin Capitalisation Rules in 2024?
Australia replaced its asset-based thin capitalisation tests with earnings-based tests. The Treasury Laws Amendment (Making Multinationals Pay Their Fair Share, Integrity and Transparency) Act 2024 (Act No. 23 of 2024) received Royal Assent on 8 April 2024 and applies to income years commencing on or after 1 July 2023, per the Act’s text on the Federal Register of Legislation. The old safe harbour, arm’s length debt, and worldwide gearing tests are gone for general entities, not modified.
The new tests are modeled on the OECD’s BEPS Action 4 final report, published 5 October 2015 and updated 22 December 2016. That report recommends a fixed ratio rule set within a 10% to 30% of EBITDA corridor, and Australia adopted the top of that range at 30%, per the OECD. Only the concepts of earnings, gearing, and third-party benchmarking survive; the tests themselves are new. Financial entities and authorised deposit-taking institutions (ADIs) keep separate regimes, per the ATO. Treasury estimated the reform would raise $720 million over four years from 2022-23, per the Parliamentary Library’s Bills Digest.
| Feature | Old regime (to 30 June 2023) | New regime (from 1 July 2023) | Source |
|---|---|---|---|
| Basis of test | Asset-based, in place since 2001 | Earnings-based, modeled on OECD BEPS Action 4 | ATO thin capitalisation rules |
| Safe harbour | Debt up to 60% of Australian assets (1.5:1 debt-to-equity) | Replaced by Fixed Ratio Test: net debt deductions capped at 30% of tax EBITDA | ATO |
| Arm’s length debt test | Higher debt if an independent lender would agree | Replaced by the elective Third Party Debt Test | ATO |
| Worldwide gearing test | Gearing tied to the worldwide group | Replaced by the Group Ratio Test | ATO |
Which of the Three New Tests Applies to Your Australian Subsidiary?
General class investors default to the Fixed Ratio Test (FRT) and may elect the Group Ratio Test (GRT) or Third Party Debt Test (TPDT) instead, per the ATO’s guidance on how the rules work. A US company’s Australian subsidiary is almost always a general class investor. The right test depends on group leverage and whether the debt is related-party or third-party.
Tax EBITDA means earnings before interest, taxes, depreciation, and amortisation, calculated on a tax basis, which differs from commercial EBITDA. The FRT replaces the old safe harbour, the GRT replaces the worldwide gearing test, and the TPDT replaces the arm’s length debt test.
| Test | What it allows | Key limit | Source |
|---|---|---|---|
| Fixed Ratio Test (default) | Net debt deductions up to 30% of tax EBITDA; denied deductions carried forward up to 15 years | Bites hardest at low or negative earnings | ATO Fixed Ratio Test |
| Group Ratio Test | Deductions based on the worldwide group’s net-interest-to-EBITDA ratio where it exceeds 30% | Helps genuinely highly-leveraged groups | ATO |
| Third Party Debt Test (elective) | Deductions only on genuine third-party debt funding Australian activities | Disallows related-party debt deductions entirely | ATO |
Do the Thin Cap Rules Apply to Your Company?
No, if your entity’s and its associates’ total debt deductions are $2 million or less for the income year. Under this de minimis threshold, the thin capitalisation rules do not apply, per the ATO. Many early-stage US expansions fall under it. Above the threshold, a US company’s Australian subsidiary is usually an inward investing general class investor.
The rules apply to entities investing or controlled across the Australian border, split into outward and inward, and separately into financial, ADI, and general classes. For most US groups setting up an Australian subsidiary, the relevant bucket is inward investing, general class.
What Are the Debt Deduction Creation Rules (DDCR)?
The debt deduction creation rules (DDCR) disallow debt deductions from certain related-party arrangements regardless of your gearing level. They target debt used to fund acquisitions of assets from associates, or distributions and payments to associates, that lack commercial substance. They apply to income years commencing on or after 1 July 2024, one year after the main tests, per the ATO.
The DDCR are the mechanism behind old warnings about “debt replacing equity” and back-to-back loans. They can deny deductions even where the Fixed Ratio Test is satisfied.
| Measure | Effective from | Source |
|---|---|---|
| Royal Assent, Treasury Laws Amendment Act 2024 | 8 April 2024 | Federal Register of Legislation |
| Earnings-based tests (FRT, GRT, TPDT) | Income years commencing on or after 1 July 2023 | ATO |
| Debt deduction creation rules (DDCR) | Income years commencing on or after 1 July 2024 | ATO |
How Do Transfer Pricing and Thin Capitalisation Interact?
Transfer pricing rules under Division 815 apply first and set the arm’s length interest rate; thin capitalisation then caps how much of the resulting deduction survives. A group can lose on either axis independently. The arm’s length debt test is gone, but arm’s length pricing still applies to whatever debt remains, per the ATO.
The ATO’s Practical Compliance Guideline PCG 2017/4, finalised 18 December 2017, on cross-border related-party financing sets a six-zone risk framework based on rate versus benchmarks, leverage, currency, and terms. An arrangement reaches the lowest-risk green zone only where the interest margin is no more than 50 basis points above the group’s external cost of funds, per PCG 2017/4. Higher scores mean higher audit likelihood. A benchmarking study justifies the rate, not the amount of debt.
Should You Fund an Australian Subsidiary With Debt or Equity?
Start with adequate equity and layer debt as the business grows. Under the new 30% tax EBITDA cap, a loss-making or low-earnings subsidiary gets little or no interest deduction, so heavy day-one debt is often wasted. Division 974, the debt/equity rules, can also recharacterise a “loan” as equity, killing deductions before thin cap even applies.
Debt also carries a cash cost that equity does not: interest paid offshore attracts a 10% interest withholding tax, subject to US-Australia treaty relief. For inbound groups, the post-reform calculus has moved toward equity or a conservative hybrid, especially for pre-profit subsidiaries whose low tax EBITDA leaves almost no room under the Fixed Ratio Test.
How Do You Structure Intercompany Loans to Survive ATO Review?
An intercompany loan survives ATO review when its amount, rate, and terms match what an independent lender would provide, the funds trace to Australian commercial activity, and contemporaneous documentation exists. Loan agreements, benchmarking studies, and board approvals are the baseline, not armor. The story has to hold together.
The ATO flags patterns that raise the burden of explanation:
- Large loans shortly after incorporation.
- Debt replacing equity without a change in business activity.
- Refinancing that increases deductions without increasing risk.
- Back-to-back loans with minimal local decision-making.
None are automatically invalid, but each shifts the burden onto you to show genuine commercial need.
Why Are Post-Entry Restructures Riskier in Australia Now?
Restructures close in time to market entry or profitability, or that shuffle debt, IP, or ownership without changing decision-making or operational reality, are more likely to be treated as tax-motivated. They can trigger Australia’s general anti-avoidance rule (GAAR), Part IVA of the Income Tax Assessment Act 1936, on top of thin cap.
Cross-border groups feel this most. Offshore funding decisions, centralised treasury, and global templates have to reconcile with local economic logic. An Australian subsidiary that looks undercapitalised, over-leveraged, or strategically passive is the most exposed under the current regime.
What Should You Do Before Expanding Into Australia?
Model your expected tax EBITDA before choosing a funding mix, check the $2 million de minimis, capitalise with equity first, benchmark any related-party rate against PCG 2017/4 risk zones, and treat restructures as board-level decisions with documented non-tax rationale. Early planning is now the difference between a defensible structure and a costly audit.
A short pre-entry checklist:
- Stress-test funding: would an independent lender lend this much, on these terms?
- Sequence equity and debt: fund with equity first, add debt as earnings grow.
- Benchmark the rate: score related-party interest against PCG 2017/4 zones.
- Board-level restructures: if you cannot explain a restructure without tax, reconsider it.
How Commenda Helps With Australian Thin Cap Compliance
Defending related-party debt in Australia requires consistent entity data, loan documentation, and transfer pricing files ready before the ATO asks. Fragmented loan balances and undocumented intercompany agreements are the real failure point: when an audit lands years later, reconstructing intent from scattered spreadsheets is slow and unconvincing.
Commenda’s transfer pricing software builds and maintains the benchmarking studies and intercompany documentation that support your interest rate, and entity management centralises your Australian subsidiary’s records and compliance artifacts in one place. Track your Australian filing deadlines with Commenda’s compliance calendar so nothing slips.
Book a demo to get a defensibility review of your Australian funding structure.
