How to Recover an Unpaid B2B Invoice in Spain When the Client Disputes the Service

An overdue invoice does not always result in a straightforward debt claim.

In many business-to-business disputes, the debtor does not simply remain silent. After receiving a payment demand, the company may argue that the work was incomplete, the quotation was never approved, the service failed to achieve the expected result or the person placing the order lacked authority.

In these cases, producing the invoice alone is not enough. The creditor must be able to establish why the invoice was issued, what was agreed, how the service was performed and when payment became due.

Can an invoice be recovered without a signed contract?

Potentially, yes.

The absence of a formally signed agreement does not necessarily prevent recovery. A commercial relationship may be evidenced through:

• accepted quotations;
• purchase orders;
• email correspondence;
• professional WhatsApp conversations;
• delivery notes;
• project reports;
• digital deliverables;
• access provided to the client;
• meeting records;
• previous invoices paid under the same arrangement;
• communications acknowledging the debt or requesting additional time.

The evidence must be assessed as a whole. An invoice created unilaterally may have limited evidential value unless it can be linked to an actual order and the performance of the relevant service.

A proper review should reconstruct the transaction chronologically: who ordered the service, what was accepted, what was delivered, when it was delivered, which objections were raised and when payment became due.

What if the client alleges defective performance?

A general complaint does not automatically extinguish the debt.

It is necessary to examine whether the objection was made during performance or only after payment became overdue, whether it identifies a specific breach and whether it concerns the entire service or only one part.

It is also relevant whether the client:

• used the delivered work;
• obtained commercial benefit from it;
• previously confirmed acceptance;
• requested further services;
• only raised objections after receiving a formal demand.

A generic statement that the service was “unsatisfactory” is not equivalent to a detailed and contemporaneous complaint supported by evidence.

The pre-action demand must be strategically prepared

A payment demand should do more than resend the invoice.

It should identify:

• the parties;
• the contractual relationship;
• the outstanding invoices;
• the due dates;
• the principal amount;
• the services performed;
• the supporting evidence;
• applicable interest and recovery costs;
• the deadline for payment or response.

Under Spanish Organic Law 1/2025, prior negotiation is generally required before civil declaratory and special proceedings, subject to statutory exceptions. The attempt must be documented and must correspond to the subject matter of the future proceedings.

The pre-action phase should therefore be designed with the potential litigation in mind.

Late-payment interest in Spanish commercial transactions

Where the creditor has complied with its contractual obligations, late-payment interest may accrue automatically once the agreed or statutory payment period expires.

In the absence of a contractual rate, Spanish Law 3/2004 applies a statutory rate based on the European Central Bank refinancing rate plus eight percentage points. For the second half of 2026, the statutory commercial late-payment rate is 10.40% per year.

The creditor may also claim:

• a fixed recovery amount of €40;
• additional documented recovery costs exceeding that amount.

Payment order or ordinary civil proceedings?

Spain’s payment-order procedure may be used for monetary debts that are due, payable, quantified and supported by documentation.

However, it is not automatically the best route. If the debtor is likely to oppose the claim by alleging defective performance, set-off, lack of authority or contractual breach, the creditor should anticipate the evidential and procedural consequences.

The appropriate route depends on:

• the amount claimed;
• the strength of the documents;
• the debtor’s registered office and solvency;
• the technical complexity of the dispute;
• the need for expert or witness evidence;
• the risk of insolvency;
• the likelihood of enforcement.

When should the company act immediately?

Delay is particularly risky when the debtor:

• stops responding;
• repeatedly asks for more time without making payments;
• changes its explanation;
• returns direct debits;
• accumulates debts with other suppliers;
• changes its corporate structure or address;
• continues using the service without paying;
• may be approaching insolvency.

Obtaining a favourable judgment does not guarantee recovery if the debtor no longer has attachable assets.

How C&Co. Legal Experts can assist

C&Co. Legal Experts advises companies, self-employed professionals and commercial suppliers on unpaid B2B debts in Spain.

Our work may include:

• legal review of the contractual evidence;
• reconstruction of the commercial relationship;
• calculation of principal and interest;
• formal pre-action demand;
• documented negotiation;
• solvency assessment;
• payment-order proceedings;
• civil litigation;
• judicial enforcement.

The objective is not to start proceedings automatically, but to identify the strategy offering the best balance between cost, available evidence, timing and realistic recovery prospects.

Is your client disputing the service and refusing to pay?

Send us a brief description of the transaction, the outstanding amount, the due date and the documents available.

After an initial screening, we will confirm whether the matter falls within the firm’s practice areas and explain how to instruct us for a legal assessment.