Late Payment Interest Calculator

Before using this calculator you should carefully refer to the terms set out in the relevant written contract. This calculator is intended for use where the terms covering late payment interest charges are based on simple interest being payable and would not require provision for compounding interest (that is, interest on interest) within the period where payment is claimed to have been overdue.

Your contact name

Your contact phone no.

Your business name

The date your correctly rendered invoice was received by the Government agency* (Format: dd/mm/yyyy)

The date payment was made by the Government agency (Format: dd/mm/yyyy)

Payment terms i.e. the number of days in which payment was to be made under your contract terms

Unpaid** amount including GST

Select daily interest rate to use

General interest charge rate
Contract specific rate***

*In calculating the interest payable, a business is required to determine the date that a correctly rendered invoice (an invoice that was rendered in accordance with the contract and with statutory requirements) was received by the Government agency. This may be determined by contacting the Government project officer or contact point. Where this date cannot be determined, a reasonable estimate should be used. The actual interest amount payable is subject to confirmation with the relevant agency that it is consistent with the terms of your contract with that agency.

**The amount which was unpaid at the time the payment was due, i.e. the amount paid late.

***You must use a daily interest rate. eg: If your contract specifies an annual interest of 5% you need to divide by 365 to determine the daily rate as per the following calculation.
5% / 365 = 0.03835616%

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