May 2026 ATO Interest Deductibility Changes: What Australian Accountants and Small Businesses Need to Check Now

May 2026 is shaping up to be a significant month for Australian accounting and tax compliance, particularly for businesses with ATO debts, payment plans, or historical lodgments still in progress. One of the most relevant and timely topics right now is the ATO interest deductibility changes affecting general interest charge (GIC) and shortfall interest charge (SIC).

From 1 July 2025, interest charged by the ATO is no longer deductible for income tax purposes. That means any GIC or SIC incurred in the 2025–26 year cannot be claimed as a tax deduction, and businesses with outstanding tax liabilities need to rethink the real after-tax cost of carrying ATO debt.

For accountants, bookkeepers and small business owners, this is not just a technical tax point. It changes how you advise clients on payment plans, cash flow, debt prioritisation and year-end tax planning. In May 2026, it is especially relevant because many practices are reviewing quarter-to-date compliance, lodging FY2025–26 activity statements, and preparing clients for EOFY decisions.

What changed with ATO interest deductibility?

The key change is simple but important: GIC and SIC incurred on or after 1 July 2025 are no longer deductible. Historically, some taxpayers could claim these charges as a business deduction, which softened the impact of overdue tax debt. That is no longer the case.

In practical terms, if a client pays ATO interest in 2025–26, that amount is now a real after-tax cost. For businesses already under pressure from rising wages, super obligations and tight margins, this can materially change the cost of deferring tax liabilities.

This makes May 2026 a timely month to reassess:

• which clients are carrying ATO debt
• whether payment plans are still affordable
• how much interest is accumulating each month
• whether refinancing or early repayment is cheaper than leaving the debt with the ATO

Why this matters now in May 2026

May sits at a critical point in the Australian compliance calendar. By this stage, many businesses have:

• lodged several BASs for the 2025–26 year
• begun planning for EOFY tax estimates
• received ATO reminders or debt letters
• entered or renewed payment arrangements

That means the effect of non-deductible interest is now becoming visible in real cash flow, not just theory. A client who was comfortable “parking” a tax bill for a few months may now be facing a higher effective cost than expected.

For accountants, this is a useful time to move from reactive compliance to proactive debt management. The earlier you identify clients with mounting ATO balances, the more options they will have.

How to explain the impact to clients

Many small business owners will only hear “ATO interest is no longer deductible” and assume it is a minor technical change. In reality, the after-tax impact can be significant.

Here is a simple way to explain it:

• If a client pays deductible interest, part of that cost is offset by a tax deduction.
• If the interest is not deductible, the full amount is borne by the business after tax.
• That makes ATO debt more expensive than many clients realise.

For example, if a business incurs $10,000 in ATO interest, the full $10,000 is now a cost to the business. Under the old rules, the tax deduction would have reduced the net cost depending on the business tax rate. That difference matters when comparing ATO debt with bank finance or private lending.

Which clients should be reviewed first?

Not every client needs the same level of attention. In May 2026, focus first on clients with any of the following risk indicators:

• outstanding BAS or IAS balances
• ATO payment plans already in place
• late lodgments from prior quarters or years
• cash flow stress or declining trading performance
• multiple entities with intercompany or director loan issues
• clients who rely on quarterly GST refunds to fund operations

These clients are most likely to be affected by rising GIC balances and may need a revised strategy before EOFY.

Practical steps accountants can take this month

If you are reviewing client files in May 2026, use a structured approach. The following checklist can help you identify exposure quickly.

1. Pull a current ATO debt position

Check each client’s current ATO balances, including:

• BAS liabilities
• PAYG withholding
• income tax debts
• super-related liabilities if applicable
• any GIC or SIC already applied

Make sure you distinguish between principal tax owed and interest charged. The deductibility change applies to the interest component, not necessarily the underlying tax liability.

2. Review any payment plans

Payment plans are still useful, but they are no longer automatically cheap. If the client is paying down ATO debt over time, the interest cost may now be fully non-deductible, which can make the arrangement less attractive than expected.

Compare the effective cost of the ATO plan against alternatives such as:

• short-term business lending
• director contributions
• cash flow restructuring
• faster debtor collection
• deferring non-essential expenditure

3. Update tax estimates

For clients carrying ATO debt, tax estimates should now reflect the fact that GIC and SIC are no longer deductible. This may affect provisional tax positions, year-end tax payable, and cash tax planning.

Where possible, build a monthly forecast that includes:

• expected BAS liabilities
• PAYG withholding
• super obligations
• ATO interest charges
• expected refunds or credits

4. Document advice clearly

Clients often remember the headline, not the nuance. Keep a file note or email summary that explains:

• what interest is being charged
• why it is no longer deductible
• what options were discussed
• what action the client chose

This is especially important if the client decides to keep a debt with the ATO despite the higher after-tax cost.

What small business owners should do before EOFY

If you run a business, May 2026 is a good time to get ahead of your EOFY tax position. The main goal is to avoid letting a tax debt quietly grow into a larger compliance problem.

Ask yourself these questions:

• Do I owe the ATO money for BAS, PAYG or income tax?
• Am I paying interest on that debt?
• Would I be better off clearing the debt before 30 June 2026?
• Have I factored in the fact that ATO interest is not deductible?

In many cases, the answer will be that it is cheaper to resolve the debt sooner rather than later. Even if full repayment is not possible, reducing the balance before EOFY can lower the amount of non-deductible interest incurred.

How this affects cash flow decisions

Non-deductible ATO interest changes the way you should think about cash flow priorities. A business might have previously been comfortable leaving a tax debt in place while investing in stock, marketing or equipment. That decision now carries a higher effective cost.

As a rule of thumb, clients should compare the after-tax cost of ATO debt with the expected return on any alternative use of cash. If the debt is costing more than the benefit of holding the money, repayment becomes the better option.

For example, a business with a $40,000 tax debt and ongoing ATO interest should consider whether that money would save more value by:

• reducing debt immediately
• funding working capital
• paying down high-interest commercial debt

Often, the ATO debt will be one of the most expensive forms of financing once the lost deduction is factored in.

Checklist for May 2026 client reviews

Here is a practical checklist you can use in client meetings or internal file reviews this month:

• Confirm all current ATO liabilities and interest charges
• Identify clients on payment plans
• Review whether interest has been incurred since 1 July 2025
• Update tax estimates to exclude deductions for GIC/SIC
• Assess cash flow capacity for early repayment
• Document advice and client decisions
• Set follow-up dates before EOFY

Where practice technology can help

For firms handling multiple clients with overdue lodgments, messy records or partial reconciliations, identifying ATO debt exposure can be time-consuming. Tools that centralise bank data, working papers and ATO tracking can make the review process faster and more reliable.

For example, platforms like Fedix can help accountants manage compliance recovery work by pulling together bank-statement data, working papers and ATO-related information in one place. Features such as MyLedger’s 1-Click Bank Reconciliation and ATO integration can save time when you are tracing liabilities, checking lodgment status and building a clearer debt picture for clients.

That does not replace professional judgement, but it can reduce the admin burden so you can focus on advice.

Final thoughts

In May 2026, the most relevant and timely issue for many Australian accounting practices is not just getting lodgments done on time. It is helping clients understand that ATO interest is now a non-deductible cost and that carrying tax debt has become more expensive.

For accountants and bookkeepers, this is a strong opportunity to add value: review debt positions, update forecasts, and help clients make better decisions before EOFY. For small business owners, it is a reminder that tax debt should be treated as a real financing cost, not just an administrative inconvenience.

If you are managing multiple overdue clients or messy compliance files, tools like Fedix may help streamline the review process. Learn more at fedix.ai.

Customer quote: “Three days of catch-up work, billed for two hours. Now we're profitable on those jobs” — Sam Malla, CPA, Sydney

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Disclaimer: This article is for general informational purposes only and does not constitute professional financial or tax advice. Always consult a qualified accountant or tax professional for advice specific to your situation. Fedix.ai provides tools to assist accounting professionals but does not replace professional judgement.