Invoice simple-interest segment review
Review simple-interest arithmetic across explicit date intervals when the entered principal or annual rate changes. Keep interval boundaries and rounding visible.
Free to use · Fictional examples · Local calculationReview entered records
AUD; explicitly verified annual simple rates only. Each row: code | start YYYY-MM-DD | end YYYY-MM-DD | principal AUD | annual percent. Start included, end excluded; contiguous rows, maximum 60. Dates 2000–2099. This does not choose a due date or establish a right to interest.
Confirm the scope, then run the review.
Worked example: split when principal changes
Fictional S1 covers 1 October up to, but excluding, 11 October: 10 days on AUD 1,000 at 12% per annum. S2 starts 11 October and ends before 21 October: 10 days on AUD 600 at 12%. With a 365-day basis, exact interest totals about AUD 5.26027, rounding once to AUD 5.26. Rounding each interval gives 3.29 + 1.97, also 5.26 in this case.
The lower second principal is a manually verified input. The page does not record a payment or decide which principal applies on a payment date. A monthly percentage cannot be pasted as an annual percentage.
Method and date boundaries
For each interval, interest equals principal × annual percentage ÷100 × calendar days ÷ the selected year-day denominator. Day counts use UTC calendar dates to avoid daylight-saving hour changes. Exact integer fractions are summed before final rounding; the report also shows the sum of individually rounded intervals. Half-cent amounts round up.
Rows must join exactly at their boundaries. A gap, overlap, duplicate code, impossible date or reversed interval stops calculation. Create a boundary whenever the applicable principal or annual rate changes. The tool cannot infer a grace period, receipt date, public-holiday adjustment, permitted rate or which day a receipt reduces principal.
Verify the actual policy separately
Queensland business guidance discusses payment terms and overdue charges. It does not supply a universal rate or approve an interest demand. The Commonwealth Finance calculator is expressly restricted to a particular procurement policy; this worksheet does not implement that policy or import its rate or payment deadline.
No compounding, monthly-rate conversion, fixed fee, minimum interest, statutory threshold, tax, collection cost or updated total debt is calculated. Do not automatically add the principal balances from different intervals: they can refer to the same invoice. An arithmetic result is not evidence that a fee is enforceable, payable or received. Obtain appropriate advice where the agreement or applicable rules are unclear.
Verify before preparing a document
Resolve the source terms and any difference before sending a statement or preparing a document. Existing invoice principal must not be invoiced again because interest arithmetic was reviewed.
Inputs are processed locally without upload, account storage or invoice-draft writes. Your browser may restore form values; protect your device and keep your own copy. Editing any input clears the prior result. A review download is working notes, not an invoice, receipt or successful invoice export.
Open the original tool for a verified documentStart the original tool without signing in. Free output has branding and usage limits. This review does not automatically create an invoice or submit a payment.
Sources and scope
Business Queensland provides payment-term context. The Department of Finance publishes a separate calculator restricted to RMG 417 procurement contracts, illustrating why policy scope must be checked. The interval method here is independent.
Sources and fictional examples reviewed 6 November 2026.