Late-payment interest on commercial invoices in Spain — Law 3/2004

Sources and assumptions

• BOE — tax year 2026, verified on September 26, 2026

  Excerpt from the source : « El tipo legal de interés de demora que el deudor estará obligado a pagar será la suma del tipo de interés aplicado por el Banco Central Europeo a su más reciente operación principal de financiación efectuada antes del primer día del semestre natural de que se trate más ocho puntos porcentuales. »

• BOE — Ley 3/2004 — tax year 2026, verified on September 26, 2026

  Excerpt from the source : « Cuando el deudor incurra en mora, el acreedor tendrá derecho a cobrar del deudor una cantidad fija de 40 euros, que se añadirá en todo caso y sin necesidad de petición expresa a la deuda principal. »

Calculation assumptions

• A commercial transaction between businesses, or between a business and a public body, within the meaning of Law 3/2004. Not covered: transactions involving consumers, interest under the rules on cheques, promissory notes and bills of exchange, damages payments, and debts caught in insolvency proceedings opened against the debtor (art. 3.2).
• You enter the ECB rate: the rate of its most recent main refinancing operation before the first day of the half-year. The Spanish ministry publishes the resulting rate in the Official Gazette every six months. If the delay spans two half-years, work out each part separately and add up only the "Interest for the period" lines: the invoice and the EUR 40 count once, because the law grants one fixed EUR 40 per late payment, not per part (art. 8.1). Do not add the two "Total you can claim" figures together.
• Simple daily interest on a 365-day year; the law does not set the divisor, this is the convention used here. The yearly interest is rounded to the cent before being spread over the days, which can shift the result by one cent.
• No interest rate agreed in the contract. An agreed rate 70% below the statutory late-payment rate is deemed abusive and the clause is void, unless shown otherwise; this rule does not apply to transactions with public bodies (art. 9.1). Working out the due date, and recovery costs above EUR 40 — which must be evidenced — are not included.
• This assumes you are entitled to the interest: the law requires you to have met your own contractual and legal obligations, and the debtor is off the hook if it proves it is not responsible for the delay (art. 6). Nor does it owe the EUR 40 if it is not responsible for the delay (art. 8.2). Where payment by instalments was agreed, interest and compensation apply only to the amounts already due (art. 6).
• You count the days late yourself, from the due date. If the contract sets no payment term, the debtor has thirty calendar days from receiving the goods or services (art. 4.1); the parties may extend it, but never beyond 60 calendar days (art. 4.3). Any clause leaving holiday periods out of the count is void (art. 2.d).