For years, businesses had a small safety net if they fell behind on tax: the interest charged by the ATO could be claimed as a deduction, softening the cost of a late or shortfall payment. That safety net is gone. From the 2025/26 income year onward, general interest charge (GIC) and shortfall interest charge (SIC) are no longer tax-deductible — and it's a change worth understanding before it costs you more than you expect.

What's Changed

Previously, if you paid tax late or had a shortfall identified after an amendment, the interest the ATO charged could be offset against your taxable income like any other business expense. Now, that interest is a pure, non-deductible cost. If you underpay your tax or miss a deadline, whatever interest accrues comes straight off your bottom line with no tax benefit to soften it.

Why This Matters More Than It Might Seem

It's easy to think of ATO interest charges as a minor administrative penalty. In practice, this change quietly increases the real cost of:

• Late BAS or tax payments — even short delays now cost more in real terms than they did last year.
• Amended assessments — if the ATO reassesses a prior return and identifies a shortfall, the interest on that gap is no longer offsetting your tax bill.
• Cash flow shortfalls — businesses that have historically used late tax payment as an informal cash flow buffer will find that approach meaningfully more expensive now.

This Connects to Other 2026 Changes

This shift lands at the same time as several other compliance changes — including Payday Super and expanded digital reporting — that increase the ATO's real-time visibility into your obligations. Reporting is becoming faster and more automated, which means the window for "catching up quietly" on late payments is shrinking, and the cost of not doing so has just gone up.

How to Protect Your Business

• 1. Treat tax deadlines as cash flow priorities Prioritize tax payments and deadlines in your schedule rather than treating them as the last item to fund each quarter.
• 2. Build a buffer for tax obligations Integrate tax buffers into your regular cash flow forecasting rather than treating tax as a flexible expense. Learn more about how we can support you with our Cash Flow Forecasting & Budgeting or Tax Planning Strategies services.
• 3. Review past assessments early If you're at risk of an amendment, the earlier an issue is identified and corrected, the smaller the interest exposure. Review prior filings with our Company, Trust & Partnership Tax Returns support.
• 4. Talk to your accountant early Connect with your accountant before a deadline slips, not after — payment plans and proactive communication with the ATO can reduce risk compared to simply missing a due date.

“ATO interest charges are no longer a tax-deductible safety net. What used to be a partially offset business cost is now a pure bottom-line loss, making proactive compliance and tax planning vital.”

The Bottom Line

This is a quiet change, but it has a real financial impact. What used to be a partially offset cost is now a straight loss to your business — which makes on-time payment and accurate reporting more valuable than ever.

If you want to review your current tax position, or put a plan in place to avoid falling behind, get in touch with our team at PHC & Associates — we can help you stay ahead of it.

Further Reading

• ATO — General interest charge and shortfall interest charge