Work Out Late-Payment Interest Invoice by Invoice — Free
Paste invoice dates and amounts with your agreed rate, and get the day count and interest per invoice on a till receipt you can send.
The proof surface
Interest is the argument nobody bothers to compute. Per-invoice day counts turn a vague complaint about late payment into a schedule a bookkeeper can check.
Why the flat version breaks
Chasing without the arithmetic
A demand without day counts reads as a complaint; a schedule with days and interest is a computation the client has to answer.
Quoting a rate you cannot point to
Statutory and contractual rates differ by jurisdiction and by contract; the receipt prints the rate you supply and makes you name its source.
Ignoring part payments
A part-paid invoice still accrues on the balance, and blending balances with full invoices overstates the total and weakens the schedule.
How to work the interest receipt
Reference, amount and date on each line; note part payments and credit notes on the same line.
The rate from your terms, and the date the calculation runs to, so the schedule can be re-run unchanged next month.
Each line shows the days outstanding and the interest that follows from it, with the total at the tear-off foot.
Send the schedule with the demand letter and name the date the figures were computed to.
What the receipt replaces
| Question | Before | On the receipt |
|---|---|---|
| How much is owed | add invoices by hand | per-invoice interest with day counts |
| What rate applies | look it up mid-argument | the rate you state, printed in the header |
| What to send | a chasing email | schedule plus a demand stub with the date run to |
Part-paid and credit-note lines are read as your own notes; the receipt prices the balance you describe rather than deciding a dispute.
Run it on the samples, right here
FIRST-LOAD
Data note: Everything runs in this browser tab on the interest receipt: your invoice dates and rates stays on this device, nothing is uploaded, and the reading is rebuilt only when you press run.
Go deeper: the companion app files the same reading as a till receipt with a tear-off foot
The article demo above runs without limits. The companion app keeps a local history, exports the rows as CSV, prints the ready-to-mail packet, and holds your drafts on this device — one free run, then $ 9 one-time for the layer that keeps filing.
The receipt and per-invoice interest are free. The paid layer prints the demand letter and keeps the ledger as invoices age.
Open the late-payment interest receipt companionBoundary
This interest receipt works only on the invoice lines, dates and the rate you agreed you paste. It does not decide what rate you are legally entitled to, does not issue a letter before a court or arbitrator, and does not chase the debt for you. The figures describe what you supplied, not what is true in the world. Confirm anything you plan to act on with your own contract terms and, for large sums, a solicitor before you rely on it.
What this is built on
- Every figure comes from the invoice lines, dates and the rate you agreed you paste; nothing is looked up, scraped or asserted as verified.
- Method: interest = invoice amount × annual rate × days outstanding ÷ 365, with the day count printed on every line
- Sample values are labelled samples — illustrative by design, not your data and not a quotation of any organisation's policy.
Before: the reader wrote off the late days. After: they can see $284.16 of interest across four invoices with the day count printed on each line.