Law firm guidesDebt recovery

Your client pays at 120 days: the interest the law owes you

Last updated 2026-09-01 · Reviewed by Jaime Piñeira Pardo, registered with the ICAM bar, no. 138826

The short answer

The payment period between businesses is thirty calendar days if nothing was agreed, and even where agreed it cannot exceed sixty. Once it expires, late interest accrues automatically on the mere failure to pay, with no need for any reminder or demand, and a fixed forty euros in recovery costs is added to the debt in every case, without express request.

You invoice a retail chain that buys from you every month. Their terms say one hundred and twenty days and, as they are your biggest client, you sign and finance the delay out of your own credit line. Last year they paid thirty eight invoices, all of them late, and you claimed nothing so as not to cause friction. Now you have run the numbers and find that the cost of that wait has swallowed the whole margin on the contract. The question is no longer whether you can claim it, but how much of what was paid late is still alive.

The case, in five lines

What is brought: Claim for the statutory late payment interest and the recovery costs compensation under Act 3/2004 on combating late payment in commercial transactions, together with the unpaid principal or on its own where payment arrived late.
Before which court: The Civil section of the Tribunal de Instancia (the first-instance court). It is a money claim between businesses, whichever route is used to bring it.
Deadline: Interest accrues once the payment period expires, which by default is thirty calendar days and can never be agreed at more than sixty. The claim must be brought before the debt becomes time barred, a period determined on the contract and the date of each invoice.
Who can bring it: The creditor in a commercial transaction who, under article 6, has performed his contractual and legal obligations and has not received the sum owed on time.
Financial risk: Article 6.b) excepts the case where the debtor proves he is not responsible for the delay, and article 8.2 then also frees him from the recovery costs compensation. Where the claim targets an active client, there is also a commercial risk to weigh before anything is moved.

Sixty calendar days is the ceiling, even if the contract says one hundred and twenty

Article 4 of Act 3/2004 sets the payment period the debtor must meet where no date was agreed in the contract: thirty calendar days after the goods were received or the services performed, even where the invoice was received earlier. And its paragraph 3 caps what may be agreed: the periods may be extended by agreement of the parties, but in no case may a period longer than sixty calendar days be agreed.

The same article places a duty on the supplier that should not be overlooked: to get the invoice or equivalent request for payment to the client within fifteen calendar days of the actual receipt of the goods or performance of the services. And where the contract set a period, receipt of the invoice by electronic means starts the clock, provided the identity and authenticity of the signatory, the integrity of the invoice and its receipt by the addressee are all guaranteed.

Interest runs by itself: no demand is needed for it to accrue

Article 5 is what changes the conversation with a late paying client. It states that the party bound to pay a money debt arising as consideration in commercial transactions falls into default and must pay the interest agreed in the contract, or that set by the Act, automatically on the mere failure to pay within the agreed or statutory period, with no need for any reminder of the due date or demand from the creditor.

The practical consequence is that a creditor who did not claim at the time has not lost the interest: it accrued anyway, invoice by invoice. Many companies discover they have spent years financing their best client for free because they believed interest was born with the demand. It is not born with the demand, it is born with the non payment, and what is needed afterwards is to quantify it precisely on each invoice and its due date.

There are only two requirements, and both are yours to check

Article 6 makes the right to late payment interest conditional on two requirements that must be met at the same time: that the creditor has performed his contractual and legal obligations, and that he has not received the sum owed on time, unless the debtor can prove he is not responsible for the delay. Nothing more. There is no requirement to have claimed earlier, to have agreed the interest, or to have protested the invoice.

The first requirement decides most cases, because it is where the debtor will build his defence: he will say the delivery was incomplete, that the service was not performed as agreed, or that documents were missing. That is why an interest claim is prepared with the same evidence of performance as the principal would be. Article 6 adds that, where a schedule of instalments was agreed, interest and compensation are calculated only on the sums that have fallen due.

The statutory rate is the European Central Bank rate plus eight points

Article 7 provides that the late payment interest is that resulting from the contract and, absent agreement, the statutory rate it sets out: the sum of the interest rate applied by the European Central Bank to its most recent main refinancing operation carried out before the first day of the calendar half year in question, plus eight percentage points. That rate applies for the six months following its fixing.

The article itself clarifies that the rate applied by the European Central Bank means the rate on its main refinancing operations in fixed rate tenders, and the marginal rate resulting from a variable rate tender. And it requires the resulting rate to be published every six months in the Official State Gazette. So the calculation is not a single figure: it is worked out in half yearly bands on each invoice, from its own due date.

Forty euros per invoice, and above that the costs you can prove

Article 8 provides that, where the debtor falls into default, the creditor is entitled to recover from him a fixed sum of forty euros, which is added to the principal debt in every case and without any express request. It is not a symbolic minimum where there are many invoices: in a commercial relationship with monthly shipments, the figure multiplies by each debt that went unpaid in time.

In addition, the same article recognises the right to claim compensation for all duly evidenced recovery costs suffered by the creditor because of the default and exceeding that amount. Duly evidenced is the key: they must be documented. And paragraph 2 sets the limit: the debtor is not bound to pay that compensation where he is not responsible for the delay in payment.

Claiming interest from an active client is a decision, not an automatism

The law grants the right, but the company chooses the moment. Some relationships are put back on track by a detailed calculation placed on the table, with no need to sue: when the client sees two years of interest plus forty euros for each invoice, the payment period tends to be renegotiated on its own. Other relationships are already broken, and then the right course is to claim everything accrued and unpaid.

In both cases the preparatory work is identical and cannot be improvised: a table with each invoice, its issue date, its statutory or agreed due date, the date it was actually paid, the days of delay, the half yearly rate applicable to each band and the resulting amount. That document is at once the argument in the negotiation and the schedule to the claim if the negotiation leads nowhere.

How we run the case, step by step

1
Check which payment period actually applies
We compare what the contract or general terms say with the sixty calendar day cap of article 4.3 and with the thirty day period applying where nothing was agreed. That comparison yields the real due date of each invoice.
2
Build the table of invoices and delays
All the invoices in the period are listed with their issue, due date, actual payment and days of delay. Without that table no claim is possible, because interest accrues and is calculated invoice by invoice.
3
Calculate the interest in half yearly bands
The statutory rate of article 7 is fixed half yearly, so a long delay crosses several bands. The corresponding rate is applied to each band and the forty euros of article 8 are added for each debt in default.
4
Gather the evidence that you performed
Article 6 requires the contractual and legal obligations to have been performed. We gather signed delivery notes, acceptance sheets, emails approving the work and proof that each invoice was sent within the fifteen days.
5
Put the calculation in front of the debtor and decide
With the table closed, payment is demanded and a short negotiating window opens. If there is no agreement, or the debtor disputes performance, the outstanding principal, the accrued interest and the recovery costs are claimed in court.

The evidence that decides the case

The contract or accepted general terms, with the payment period clause to be tested.
Each invoice with its date, and proof it was sent within fifteen days of delivery.
Signed delivery notes or acceptance sheets proving the date of receipt or of performance.
The bank statement fixing the actual payment date of each invoice paid late.
The half yearly publication of the statutory late payment rate in the Official State Gazette for each band.
Documents evidencing recovery costs above the forty euros for each debt in default.

What closes the door

Believing that interest is lost if it was not claimed at the time. Article 5 accrues it automatically on the mere failure to pay, with no reminder or demand.
Accepting a one hundred and twenty day period in writing and treating it as valid. Article 4.3 prevents in every case agreeing a period longer than sixty calendar days.
Invoicing late. Article 4.1 requires the invoice to reach the client within fifteen calendar days of delivery, and your own delay weakens the whole claim.
Claiming a single approximate figure of interest. The calculation is made invoice by invoice and in half yearly bands, and a round number invites the whole amount to be disputed.
Forgetting the forty euros per debt. Article 8 adds them in every case and without express request, and in relationships with many invoices they add up.

The law that applies

Art. 4 Ley 3/2004. It sets the payment period: thirty calendar days from receipt of the goods or performance of the services if no other was fixed, with the supplier obliged to send the invoice within fifteen calendar days. Acceptance or verification procedures may not exceed thirty days, and no agreement between the parties may exceed sixty calendar days. BOE-A-2004-21830
Art. 5 Ley 3/2004. It establishes automatic accrual: the party bound to pay a money debt arising as consideration in commercial transactions falls into default and must pay the agreed or statutory interest on the mere failure to pay within the agreed or statutory period, with no need for any reminder of the due date or demand from the creditor. BOE-A-2004-21830
Art. 6 Ley 3/2004. It requires two simultaneous conditions for interest to be demanded: that the creditor has performed his contractual and legal obligations, and that he has not received the sum owed on time, unless the debtor proves he is not responsible for the delay. With instalment schedules, interest and compensation are calculated only on the sums that have fallen due. BOE-A-2004-21830
Art. 7 Ley 3/2004. It sets the rate: that of the contract and, absent agreement, the statutory one, being the rate applied by the European Central Bank to its most recent main refinancing operation before the first day of the calendar half year, plus eight percentage points. It applies for the following six months and is published half yearly in the Official State Gazette. BOE-A-2004-21830
Art. 8 Ley 3/2004. It grants the creditor, where the debtor falls into default, a fixed sum of forty euros added to the principal debt in every case and without express request, plus compensation for all duly evidenced recovery costs exceeding that figure. The debtor does not owe it where he is not responsible for the delay. BOE-A-2004-21830

Each article checked against the consolidated text published in the BOE (the Spanish official gazette).

Frequently asked questions

I signed terms with payment at 120 days. Am I bound by them?

Article 4.3 allows the statutory periods to be extended by agreement, but adds that in no case may a period longer than sixty calendar days be agreed. That limit does not depend on your having accepted it, nor on the clause sitting in the client's general terms. The first thing reviewed in these matters is precisely that agreement, because the due date of every invoice depends on it.

They have already paid me, though late. Can I still claim anything?

The interest accrued when the delay happened, not when you claim it, because article 5 makes it automatic on the mere failure to meet the period. Once the principal has been paid late, what remains alive is the interest for the days of delay on each invoice and the fixed forty euros of article 8 for each of the debts that were paid late.

Are the forty euros per client or per invoice?

Article 8.1 ties them to the debtor's default and adds them to the principal debt, so the reference point is each debt unpaid in time and not the commercial relationship as a whole. In a supply arrangement with monthly invoicing that difference is substantial, and that is why the invoice table is built in detail before anything is quantified and before payment is demanded.

The client says the delay is not his fault. Is he off the hook?

Only if he proves it. Article 6.b) excepts the case where the debtor can prove he is not responsible for the delay, and article 8.2 then also frees him from the recovery costs compensation. The burden is his, not yours, and a general explanation about cash flow or about third party delays rarely fits that exception, which is examined case by case.

Will claiming interest cost me the client?

It is a commercial decision taken with the figures in front of you, not a legal automatism. In many live relationships, presenting the detailed calculation serves to renegotiate the payment period going forward, without claiming the past. In relationships already damaged, waiting only lets the amount grow while the debt moves closer to becoming time barred.

This guide explains how the action works in general. It does not replace the study of your own case: deadlines depend on when things happened and on what you have done since.