Default interest (úrok z prodlení)
Penalty interest the debtor pays on an overdue amount for each day of delay (§ 1970 of the Civil Code). Its rate is set by Government Decree No. 351/2013 Coll.: per year, the ČNB 2T repo rate in force on the first day of the calendar half-year in which the delay began, plus 8 percentage points. For delays arising in the second half of 2026 that makes 11.75 %.
Example
A client with a CZK 4,000,000 mortgage at 5.00 % pays the CZK 23,384 instalment 30 days late. Default interest at 11.75 % a year (repo 3.75 % + 8 pp) comes to CZK 23,384 × 11.75 % × 30/365 ≈ CZK 226. The sum itself is small; the arrears record in the credit register does more harm.
In practice
On top of default interest, the bank usually charges reminder fees under its rate sheet. Repeated or long arrears lead to an entry in BRKI (the banks' credit register), loss of rate discounts and eventually acceleration of the loan. Paying late “just once” shortly before refinancing is a costly habit, because the new bank will see the register entry and price its offer accordingly.
How it differs
Default interest punishes late payment, whereas the contractual interest rate is the price of borrowed money. An early repayment fee covers the opposite case, paying earlier than the contract provides, and the law caps it at 1 % of the amount prepaid.
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