GDP adjustment for 2026–27 GST and PAYG instalments

From 1 July 2026, the gross domestic product (GDP) adjustment factor will change to 5% and will apply for the 2026–27 income year. This is used to work out quarterly GST and PAYG instalment amounts:

• Taxpayers with a substituted accounting period (SAP) whose income year commenced on 1 January, 1 February or 1 March 2026 will continue to use the 2025–26 GDP adjustment of 4%. This is because their income year started before the current year’s GDP adjustment of 5%.
• Taxpayers starting their income year from 1 April 2026 will have a GDP adjustment of 5%.