Invoice due date and late payment interest
From the invoice date and the agreed terms to the exact day it falls due, holidays included, with the late payment interest when the payment is already overdue.
1. The invoice
The amount is only used for the interest: if you just need the due date you can leave it as it is.
2. Payment terms
3. Saturdays, Sundays and holidays
4. Late payment interest, if it is overdue
The table stops at the first half of 2026. For later half years the tool uses the rate typed above and says so: the official figure for the current half year is published by each member state.
Everything is worked out inside your browser: dates and amounts are never sent anywhere.
The two readings of 60 days end of month
It is the wording that trips up most accounts departments. Take an invoice dated 15 January 2026 with 60 days. Counting the days from the invoice date gives 16 March. Counting the days and then moving to the end of that month gives 31 March. Going to the end of the invoice month first and then counting 60 days gives 1 April. Same wording, three different dates. This tool works out all three, but the last word belongs to the contract or the purchase order: if it is not written down, ask the supplier before a reminder tells you.
When the clock starts
Not on the date printed on the invoice but on its receipt, and when the goods arrive later the clock starts from delivery (art. 3 of Directive 2011/7/EU). The default term is 30 days; between businesses the parties may stretch it, but beyond 60 days it must be expressly agreed, and it is void anyway when it is grossly unfair to the creditor (art. 7). For public authorities the cap is 30 days, 60 only for public health entities. The days are calendar days, not working days: weekends in the middle count, they do not stop the clock.
When the due date falls on a holiday
Most national laws postpone a term falling on a public holiday to the first following working day, so the tool can move the date forward for you. Since public holidays differ from country to country, this page skips weekends only and lets you list your own holidays in the field. Saturday is not a public holiday, but banks do not settle transfers on it: the checkbox is on by default because that is what happens in practice, and you can untick it when the contract works in calendar days.
How late payment interest is worked out
It runs automatically from the day after the due date, with no reminder and no formal notice (art. 3 of Directive 2011/7/EU). The rate is the ECB reference rate plus at least 8 points (art. 2), and here is the detail that ruins hand made figures: the rate in force on the first day of the half year applies for all six months, so a long delay has to be split half year by half year, each with its own rate. The tool does that and shows you the table. Each slice is amount × yearly rate × days ÷ 365. The 40 € fixed recovery sum of art. 6 is due automatically and does not stop you from claiming higher recovery costs when you can document them.
What this tool does not know
It does not know whether the contract changes the terms, whether the invoice is disputed, whether an acceptance or verification procedure is running (which can move the starting point) or whether credit notes exist. The built in rates stop at the first half of 2026: for later half years it uses the value you type and says so in a warning, because the official figure is published by each member state. Some countries set higher interest or extra rules for specific sectors, such as food supplies. This is an informative tool, not legal advice.