Penalty Interest Calculator

Entered Rates and Statutory Presets

Choose Entered annual rates if your debt has a rate set by an agreement. Enter the opening rate and the date each new rate takes effect. Use the counting and compounding terms in the agreement. This gives an estimate using the rates you supplied.

Choose NSW overdue transfer duty for unpaid NSW transfer duty. The preset uses the quarterly rates from Revenue NSW. The schedule selector shows the first and last days covered.

Choose Victorian civil judgment when the judgment debt carries the rate set by the Victorian Attorney-General under the Penalty Interest Rates Act 1983. The preset covers the two most recent rate periods in the Supreme Court of Victoria schedule. Use the first date that carries interest under the order. Use an entered rate for an order that sets a different rate.

Days, Rate Periods and Payments

For simple interest, multiply the unpaid principal by the annual rate as a decimal. Multiply that amount by the number of days in the period, then divide by the annual day count. With daily compounding, each day’s interest is added to the balance for the next day.

With entered rates, you choose whether each endpoint counts. A same-day period counts once if both endpoints are included. A fixed annual basis divides by 360 or 365 every year. The 365 or 366 option uses the number of days in each calendar year. Any counted period that includes a leap day counts that day.

NSW duty interest starts the day after the due date and counts the final day. The preset uses simple interest and divides by 365, including in leap years. The Victorian civil judgment estimate counts the first chargeable date and the final day. It uses simple interest and divides by 365 or 366 according to the calendar year.

A new rate applies from its effective date. The calculator charges interest on a payment date at that day’s opening balance and reduces principal for the following day. A final-day payment reduces the outstanding principal in the result. Enter only the part of each payment credited to principal. The breakdown keeps cents so you can check how each period contributes to the estimate.

Overdue Stamp Duty Interest

Enter the unpaid duty and the due date from your assessment. Use the date you want to calculate through or the date the duty was paid. Enter any partial payments using the dates and principal amounts shown on your account.

Revenue NSW charges daily interest once the due date passes. The rate combines a market component that can change each quarter and an 8% premium. Earlier interest does not earn interest. Under the NSW Taxation Administration Act 1996, interest below $20 is not payable.

The estimate uses the duty already assessed. Penalty tax is a separate charge. The Chief Commissioner can remit some or all of the interest. The preset applies the full scheduled rate, so use the assessment for the amount actually charged if Revenue NSW grants remission or adds a separate penalty.

Worked Interest Breakdown

The example starts with $36,500 in unpaid transfer duty. Five chargeable days fall before the October 2026 NSW rate change. After another five days, a $11,500 payment reduces principal to $25,000 for the last ten days.

The Revenue NSW duties interest calculator returns $124.70 for the first ten days when the whole duty remains unpaid. Adding the last row gives $210.38 in interest. The remaining $25,000 principal brings the estimate to $25,210.38 before the headline rounds to whole dollars.

With the same dates and payment, a debt at an entered 10% simple rate on a 365-day basis accrues $100 before the payment and $68.49 after it. The $168.49 interest brings the total to $25,168.49.