Calculator
Polish late-payment interest calculator
Choose civil late-payment interest or interest for a qualifying commercial transaction. Commercial mode distinguishes ordinary debtors from public healthcare entities. The existence of an invoice alone does not determine the legal regime.
Calculator
Enter data
Automatic rates: 1 January 2025–22 September 2026; commercial rates only from 1 January 2026. Fields marked with an asterisk are required.
How to use the calculator
- Enter the effective due date after any applicable weekend/holiday adjustment. Accrual starts the following day and includes payment day.
- Automatic mode splits periods on rate changes. Manual mode assumes one constant rate; calculate separate intervals if it changes. Do not confuse maximum and statutory rates.
Calculation details
Formula and calculation method
Sum of principal × annual percentage rate × days / 36500; actual days with a fixed 365 denominator. Period amounts are not rounded before summing. Civil result to cents; tax result to whole PLN after testing the unrounded total against PLN 8.70.
Worked example
PLN 10,000 civil debt due 4 March 2026 and paid 14 March: ten days at 9.25% gives PLN 25.34. This rate must not be substituted for commercial-transaction interest.
Limitations
- Automatic rates: 1 January 2025–22 September 2026; commercial rates only from 1 January 2026.
- One unchanged debt, without partial payments, compounding, collection charges, accrual suspensions or limitation-period assessment. Selecting a mode does not establish legal entitlement.
Sources
- ZUS — historical civil interest rates
- Polish Justice Minister — 2026 late-payment interest notice
- Commercial interest H1 2026 — MP 2025/1257
- Commercial interest H2 2026 — MP 2026/642
Engine version: 1.0 · Last reviewed: 22 September 2026
Frequently asked questions
What does this tool cover?
Choose civil late-payment interest or interest for a qualifying commercial transaction. Commercial mode distinguishes ordinary debtors from public healthcare entities. The existence of an invoice alone does not determine the legal regime.
Which assumptions should I verify?
Automatic rates: 1 January 2025–22 September 2026; commercial rates only from 1 January 2026. One unchanged debt, without partial payments, compounding, collection charges, accrual suspensions or limitation-period assessment. Selecting a mode does not establish legal entitlement.
Are entered values stored?
Calculations run locally in your browser. Entered identifiers, amounts and results are not stored or sent to analytics.