If you’re carrying an Australian Taxation Office (ATO) debt there is a good chance that it will cost you even more from 1 July 2025 onwards. This is because from 1 July 2025 two types of interest charges imposed by the ATO are no longer deductible.

What are the interest charges?

There are two main types of interest that are charged by the ATO. These are:

• General Interest Charge (GIC): This applies when you pay your tax liability late. The ATO applies GIC to encourage tax liabilities to be paid on time and ensure taxpayers who pay late don’t have an unfair advantage over taxpayers who pay on time. GIC is calculated on a daily compounding basis on the overdue amount. The GIC annual rate for the July – September 2025 quarter is 10.78%.
• Shortfall Interest Charge (SIC): This is applied when there is a shortfall in tax paid because of an amendment or correction to your tax assessment. SIC is also calculated on a daily compounding basis. The SIC annual rate for the July – September 2025 quarter is 6.78%. The ATO applies SIC to the tax shortfall amount for the period between when it would have been due and when the assessment is corrected.

What’s changing?

Historically, both GIC and SIC amounts could be claimed as a deduction. This has meant that the net after-tax cost of the interest charges has been reduced for taxpayers who have a positive income tax liability for the relevant income year.

However, the Government has passed legislation to ensure that GIC and SIC amounts incurred on or after 1 July 2025 are no longer deductible, even if the interest relates to a tax debt that arose before this date.

As these interest charges are no longer deductible, this means that the after-tax impact of the charges is higher for many taxpayers. The impact becomes greater as your tax rate increases.

For example, let’s take a look at two individuals who have the same level of tax debt owed to the ATO and the same level of tax debt owed to the ATO and the same GIC liability of $1,000 for a particular income year:

• Sally is a high income earner and subject to a 45% marginal tax rate (ignoring the Medicare levy). Under the old rules the net cost of the interest charge was only $550 because she could claim a deduction for the GIC amount and this reduced her income tax liability by $450. Under the new rules no deduction is available and the full cost to Sally will be $1,000.
• Adam is subject to a 30% marginal tax rate (again, ignoring the Medicare levy). Under the old rules the net cost of the interest charge was $700 because he could reduce his income tax liability by $300 by claiming a deduction for the GIC amount. As with Sally, under the new rules no deduction is available for the GIC and the full cost to Adam is $1,000.

What can I do to minimise the impact of this change?

The simple answer is to pay down ATO debt as quickly as possible. As you can see, the GIC rate is relatively high and continues to accrue on a daily basis until the debt is paid off.