The Tax Office Just Made Tax Debt More Expensive
Many Australians are surprised to learn that the Australian Taxation Office (ATO) charges interest when tax debts remain unpaid.
Known as the General Interest Charge (GIC), this interest applies when tax liabilities are not paid by their due date. For many years, taxpayers who incurred GIC could generally claim a tax deduction for the interest charged, helping to reduce the after-tax cost of carrying tax debt.
However, that is no longer the case.
Since 1 July 2025, General Interest Charges (GIC) and Shortfall Interest Charges (SIC) imposed by the ATO have no longer been tax deductible. While the change has received relatively little attention outside of tax circles, it has significantly increased the true cost of carrying unpaid tax liabilities and has important implications for business owners, investors and self-employed Australians.
Let’s consider a simple example.
Imagine a taxpayer owes the ATO $100,000 and incurs interest on the outstanding balance. Under the previous rules, the interest charged could generally be claimed as a tax deduction, reducing the effective after-tax cost. Today, every dollar of GIC must be paid entirely from after-tax income.
The result is straightforward: tax debt has become materially more expensive.
This change reflects a broader policy objective of encouraging taxpayers to pay tax liabilities on time. Historically, some taxpayers viewed the ATO as a relatively flexible lender, particularly where interest costs were deductible and alternative financing options were limited. The removal of deductibility changes that equation considerably.
For many taxpayers, the after-tax cost of GIC may now be higher than alternative borrowing options available through banks, mortgage facilities or business lending arrangements. While every situation is different, the gap has become large enough that outstanding tax debts should no longer be ignored as simply another balance sitting on the books.
The change also highlights the importance of cash flow planning. Whether you are an employee with investment income, a self-employed professional, a property investor or a business owner, ensuring sufficient funds are set aside for upcoming tax obligations can help avoid unnecessary interest charges and financial stress.
For those already carrying tax debt, early engagement with the ATO remains important. Payment plans may be available and can assist taxpayers who are experiencing temporary financial difficulties. Waiting until the debt becomes unmanageable often limits available options and increases overall costs.
Importantly, repaying tax debt should not occur in isolation. Decisions should be considered alongside liquidity requirements, investment opportunities, debt reduction strategies and broader financial objectives. However, the removal of tax deductibility means that any analysis should now use the full after-tax cost of the interest being charged.
The days of treating ATO debt as a relatively tax-effective source of funding are over.
SWU Group Insight
Many Australians focus on the interest rate charged by the ATO without considering the loss of the tax deduction. Since 1 July 2025, the effective cost of carrying tax debt has risen significantly because GIC and SIC must be paid from after-tax dollars. Investors, business owners and self-employed individuals should review any outstanding tax liabilities and carefully assess whether alternative funding arrangements may be more cost-effective. In a higher-interest-rate environment, proactive tax planning and cash flow management can help preserve wealth and avoid unnecessary costs.