Late-payment interest — what you should know
When a counterparty pays late, you're entitled to charge interest. In business-to-business transactions, the default basis is statutory interest for delay in commercial transactions (the Act on Counteracting Excessive Payment Delays). The parties may also apply statutory interest for delay under the Civil Code. Both rates depend on the NBP reference rate.
This calculator computes interest separately for each period a rate was in effect (when the overdue period spans a rate change) — so the result is exact, not averaged.
Frequently asked questions
What interest is a company entitled to for a late payment?
In commercial transactions: the NBP reference rate + 10 percentage points (non-public debtor) or + 8 percentage points (public healthcare entity). Statutory interest for delay under the Civil Code is the NBP rate + 5.5 percentage points.
What are the current interest rates?
As of 6 July 2026: commercial transactions — 13.75% (non-public debtor) and 11.75% (healthcare entity); statutory interest for delay (Civil Code) — 9.25%. Rates change along with the NBP reference rate.
From when to when is the interest calculated?
From the day after the payment due date to the day of payment (inclusive). Each day of delay accrues a portion of the annual rate.
How is the interest calculated in this tool?
Using the formula: amount × number of days × annual rate / 365, calculated separately for each period the given rate applied. The result is for guidance only — the binding basis depends on the contract and the law.