PAYG instalments are one of those tax obligations that often catch business owners off guard—especially when the amount suddenly increases. The key to avoiding surprises is understanding that some changes are automatic, while others depend on when your latest tax return is processed.
What Are PAYG Instalments?
PAYG (Pay As You Go) instalments are regular prepayments towards your expected income tax liability. Instead of facing a large bill at year-end, you pay tax in quarterly instalments throughout the year.
You’ll typically enter the PAYG instalment system if you earn business or investment income and your tax payable exceeds a certain threshold. This applies to sole traders, companies, trusts, and individuals with non-salary income such as rent or dividends.
How Are They Calculated?
The ATO calculates your instalments based on your most recently lodged tax return. You’ll either pay a fixed amount each quarter or a percentage of your income (instalment rate), with most growing businesses using the rate method.
Why Do PAYG Instalments Increase Each Year?
Every year, the ATO applies an automatic “uplift factor” to PAYG instalments. This is based on economic data (such as GDP) and is designed to keep your instalments in line with expected growth in income.
Importantly, this uplift happens at the start of each financial year and is reflected from the September quarter instalment onward. So even if your business hasn’t changed, you may still notice a slight increase compared to the previous year.
Why Do Bigger Changes Happen Mid-Year?
More significant jumps—or even being added into the PAYG instalment system mid-year—usually come down to timing.
When you lodge your most recent tax return, the ATO reassesses your position using updated income figures. If your latest return shows higher profits, your instalment rate or amount may be increased accordingly. If you weren’t previously in the system, you may be brought in at that point.
This is why some taxpayers see a noticeable spike in instalments partway through the year—it’s not random, it’s triggered by the lodgement of their prior year tax return.
Can You Adjust Your Instalments?
If your current year income is expected to be lower, you can vary your PAYG instalments. However, caution is needed—underestimating can lead to interest charges if your final tax bill is higher than expected.
The Bottom Line
PAYG instalments increase for two main reasons: an automatic annual uplift from the September quarter, and updates triggered when your latest tax return is lodged. Understanding this timing helps explain why your payments can suddenly jump—and puts you in a better position to plan ahead.
