Guide
Twelve common GST mistakes and how to avoid them
The errors that most often cost small businesses money, with a checklist for fixing them.
Calculation errors
Taking 10% of a GST-inclusive price instead of dividing by 11 overstates the GST. Check your formulas and your accounting software settings.
Category errors
Treating input-taxed supplies like GST-free, claiming credits on private items, and charging GST on GST-free sales are the most common category mistakes. Review each product and service code.
Documentation errors
Claiming credits without a valid tax invoice, invoices missing ABNs, and invoices that do not say tax invoice, can all lead to disallowed credits.
Timing errors
Using the wrong accounting method, claiming credits in the wrong period, and missing credits entirely, all cause misstatements. Missing registration on time is also costly.
Reporting errors
Entering figures into the wrong labels, mixing GST-inclusive and exclusive amounts, forgetting to include adjustments, and lodging late. Reconcile before you lodge.
A practical checklist
Before each BAS, reconcile your bank accounts, review every transaction with an unusual GST code, check that large purchases have valid tax invoices, check private use, and compare this quarter's figures with last quarter's to spot odd movements. Keep a note of any judgement calls you made so that you can explain them later.
← Back to Glossary Open the GST calculator Browse the glossary