Legal and late-payment interest calculation in Belgium

How the calculation works

1. Claim and period. The principal, the first day of interest (formal notice, due date or the day after the payment term) and the last day (payment or day of the calculation), both included.
2. Rate. Four choices: the legal rate, set per calendar year (law of 5 May 1865, art. 2, § 1); the commercial transactions rate, set per half-year (law of 2 August 2002, art. 5); the commercial rate for a contract concluded from 7 August 2002 to 15 March 2013; a contractual rate you enter.
3. Periods. The tool splits the time at each rate change (1 January for the legal rate, 1 January and 1 July for the commercial rate) and at each partial payment.
4. Interest. For each period: principal × rate × exact number of days ÷ 365, rounded to the cent.
5. Partial payments. Each payment goes first to the interest due, then to the principal (Civil Code art. 5.210).
6. Flat compensation. For a commercial transaction, you can add the €40 recovery compensation per invoice paid late (law of 2 August 2002, art. 6).

The statement (days, rate, principal and interest per period) exports to PDF, Word and CSV.

Legal basis

• Legal rate: law of 5 May 1865, art. 2, § 1. It is the average 12-month Euribor of December of the previous year, rounded up to the next quarter point, plus 2 points. It is 4.50 % in 2025 and in 2026.
• Commercial rate: law of 2 August 2002 on combating late payment, art. 5. It is the ECB main refinancing rate on 1 January or 1 July, plus 8 points, rounded up to the next half point. It is 10.50 % for both half-years of 2026.
• Civil Code: arts. 5.207 (interest on interest), 5.210 (imputation of payments) and 5.240 (moratory interest).
• Legal interest rates published by the FPS Finance.

Points of attention

• Moratory interest runs from the formal notice, unless the law or the contract makes it run automatically (Civil Code art. 5.240).
• Between enterprises, and with public authorities, interest runs automatically from the day after the payment term: 30 days by default, at most 60 days by contract.
• The €40 compensation is due automatically, without formal notice, as soon as interest is due at the commercial rate: for each invoice paid late, also when several invoices are claimed together (Court of Justice of the European Union, 20 October 2022, C-585/20).
• For a contract concluded from 7 August 2002 to 15 March 2013, the original rule of the 2002 law applies until 15 March 2015: the ECB rate plus 7 points, rounded up to the next half point. From 16 March 2015, the general rate and the €40 compensation apply (law of 22 November 2013, art. 12).
• Interest due bears interest only after a written formal notice or a specific contract, and for interest due for at least a full year (Civil Code art. 5.207).

What the tool does not do

• It covers the legal rate from 2002 to 2026 (7 % until 2006, 6 % in 2007, 7 % in 2008, 5.50 % in 2009) and the commercial rate until 31 December 2026: from 16 March 2013 for contracts concluded since that day, from 7 August 2002 for contracts concluded from 7 August 2002 to 15 March 2013. The 2027 rates are not yet published: the tool says so, and you can use a contractual rate.
• It does not cover contracts concluded before 7 August 2002.
• It counts exact days over a 365-day year, leap years included. This is the practice; no text sets this basis.
• It does not compute interest on interest, tax interest or the rules of Book XIX of the Code of Economic Law for consumer debts.
• The statement of several invoices, each with its own first day of interest, is a firm feature, free with a verified e-mail address; it does not compute partial payments.

Verification

The rates and rules were checked on 5 October 2026. The tool assists the lawyer, who remains responsible for the calculation and for checking the applicable rule.