Late Payment Interest Calculator
Enter the unpaid amount, the due date and the date you want to calculate to. The calculator uses the base rate published by the Deutsche Bundesbank for each half-year and adds 9 percentage points between businesses or 5 when the debtor is a consumer.
About this tool
Default Interest Under German Law
The calculator applies §§ 286 and 288 BGB to an overdue invoice and splits the time into periods with the Deutsche Bundesbank's base rate.
Business or Consumer
Nine percentage points above the base rate between businesses, five when a consumer owes the money.
Every Rate Change Counted
The base rate changes on 1 January and 1 July; claims that span a change are calculated period by period.
€ 40 Flat Fee
Added automatically when the debtor is a business, as § 288 (5) BGB allows.
How to use it
- Enter the unpaid amount (gross), the due date and the date to calculate until.
- Choose the debtor: Business or Consumer.
- Read the default interest with the days in default and the annual rate.
- Check the flat fee and the total claim.
- Look at Calculation by period to see how each half-year's base rate was applied, and use the figures in your reminder.
Frequently asked questions
What is the statutory late payment interest in Germany?
Under § 288 BGB it is the base rate (Basiszinssatz) plus 9 percentage points when no consumer is involved, and plus 5 points for consumers. Since 1 July 2026 the base rate is 1.52 %, so 10.52 % and 6.52 % per year.
From when does default interest run?
From the day after a fixed due date has passed, or after a reminder. This calculator counts the actual days from the day after the due date up to and including the end date, divided by 365.
When can I charge the € 40 flat fee?
§ 288 (5) BGB grants a flat fee of € 40 when the debtor is in default and is not a consumer. It is charged once per claim and set off against later collection costs.
Is my financial data uploaded to any server?
No. Every calculation, PDF and XML file is produced inside your browser tab with JavaScript and WebAssembly. Nothing is uploaded, stored or logged — the tool also keeps working offline.
Do I have to send a reminder first?
Not if the invoice had a fixed due date: default starts the day after it. Without one, default starts with a reminder, or 30 days after the invoice was received — for consumers only if the invoice pointed this out.