Interest calculator

Simple interest on a principal sum, period by period: the legal interest rate, the late-payment rate for commercial transactions, or a fixed agreed rate.

Principal (EUR)

FromUntil (not included)

Today by default. Days are counted from the start date to the end date.

Interest rate

Legal interest (civil matters)Law of 5 May 1865, set per calendar year.Commercial transactions (B2B)Law of 2 August 2002 on combating late payment in commercial transactions, art. 5; set per semester.Agreed rateA fixed yearly rate from the contract.

Rates on file up to and including 31/12/2026.

Payments

The debtor's partial payments, with date and amount. They are imputed by the rules below.

Imputation and capitalisation

Imputation within a claim

Costs first, then interest, then principalArt. 1254 old Civil Code and art. 5.210 Civil Code: interest before principal unless the creditor agrees. Costs first is the usual practice (check).Principal first (by agreement)Only if the creditor agrees. Then interest, then costs.

Capitalise interest (anatocism)Art. 1154 old Civil Code, art. 5.207 Civil Code (check): only after a court claim (under Book 5 possibly also a formal notice) or a special agreement, and for interest due for at least a full year. On that date and every anniversary, the unpaid interest of a claim running for at least a year is added to its principal.

Method: principal × rate × days / 365, also in a leap year, split at every change of rate. Neither law sets the day count; this is the usual practice, but check it for your case. Each period is rounded to the cent.

No capitalisation by default (anatocism, art. 1154 old Civil Code, art. 5.207 Civil Code): interest on interest needs a court claim or a special agreement for at least a full year's interest. Only switch it on if so.

Source: FOD Financiën (financien.belgium.be), bekendgemaakt in het Belgisch Staatsblad

A tool, not legal advice. Check the rates in the Belgian Official Gazette.