GST Late Fee and 18% Interest: How They Are Calculated
File your GST return late and you owe both a daily late fee and 18% annual interest on tax due. Here's how each is calculated.
Two costs for a late GST return
Miss a GST filing deadline and there are two separate charges:
- Late fee — a fixed amount per day of delay (per Act, split across CGST and SGST), subject to a cap.
- Interest — 18% per annum on the net tax liability, charged for the period of delay.
The GST Late Fee Calculator works out both from your figures.
How the interest works
Interest accrues only on the tax actually due, calculated day by day:
- Interest = tax due × 18% × (days late ÷ 365)
So a larger liability or a longer delay both push the cost up quickly.
How the late fee works
The daily late fee depends on whether the return is a nil return or has tax due, and is capped at a maximum. Enter the days late and the tool applies the standard rate.
How to use it
- Enter your tax liability for the period.
- Enter how many days the return is late.
- The tool returns the late fee plus 18% interest.
Avoid the charge entirely
The cheapest late fee is the one you never pay. Keeping returns ready on time is far simpler with organised books — see Pyalm's full set of free finance tools.