Guide · updated November 2026
Can you charge interest on late invoices?
Only if your contract or invoice terms said so. If they didn't, keep your demand to the amount owed. Courts and tribunals may award interest under their own rules.
How to calculate simple interest
Amount × rate × days overdue ÷ 365. For example, $3,850 at 10% for 44 days is about $46.41.
Set terms for next time
- State the due date and an interest rate for overdue amounts
- Include recovery costs
- Get the customer's acceptance in writing
Owed money right now?
Do the free debt check, then get every reminder, the letter of demand and the small claims pack written for you, from A$29. You keep 100% of what you recover.
Free debt check Chase my invoiceMore: Letter of demand for an unpaid invoice: what to include · Unpaid invoice reminder emails that actually get paid · Recovering an unpaid invoice in NSW · Recovering an unpaid invoice in Victoria · QCAT minor debt claims for unpaid invoices · Payment plan agreements for overdue invoices · Statutory demands: a cautious explainer