Formal claim to the lender of your revolving credit card (tarjeta revolving), by burofax with proof of receipt

Legal basis and things to bear in mind

• The claim is addressed to the customer service department that every financial institution is required to have under artículo 29 de la Ley 44/2002, on measures to reform the financial system. That department is free of charge and has a duty to deal with and decide in writing on the claim you submit; artículo 29.5.b) sets it a deadline of one month from submission to do so.
• The main legal basis of the written document is the Ley de 23 de julio de 1908 on the nullity of usurious loan contracts. Its artículo 1 declares void any loan in which an interest rate is stipulated that is notably higher than the normal rate for money and manifestly disproportionate to the circumstances of the case.
• If the contract is declared void for usury, artículo 3 of that same law requires you to return only the sum you received: everything you have paid above that capital, including interest, fees and linked insurance, has to be paid back to you.
• In the alternative, the written document argues that the contract terms are unfair under artículos 82 y 83 of the consolidated text of the Ley General para la Defensa de los Consumidores y Usuarios (General Act for the Protection of Consumers and Users), which declare automatically void any terms not individually negotiated that cause a significant imbalance to the consumer's detriment, as well as terms incorporated in a way that is not transparent.
• The nullity of the contract does not expire, but the return of the money does have a limit in time: artículo 1964.2 del Código Civil sets the deadline for personal actions at five years, and restitution is counted instalment by instalment. That is why what can be claimed reaches back five years before the date of the claim, and each month that passes leaves one instalment out.
• Artículo 1973 del Código Civil provides that an out-of-court claim interrupts the limitation period. Interrupting is not freezing the clock: the deadline starts counting again from zero on the day the lender receives your written document. That is why it is sent by burofax with proof of receipt, because the proof of receipt is the evidence of that date.
• Once the month has run out with no reply, or with a negative reply, you can turn to the Banco de España complaints service, provided for in artículo 30 de la Ley 44/2002. You should know that this service decides by means of reasoned reports that do not bind the lender and that are not administrative acts open to appeal, so they do not replace a court claim.
• If court proceedings should be needed later on, the law requires an attempt at agreement first: artículo 5 de la Ley Orgánica 1/2025 makes prior negotiation a requirement for the court to admit the claim, and this claim serves precisely to prove that attempt. The lawsuit, if it becomes necessary, is engaged separately.
• No claim guarantees a refund, because the lender can reject it. What is assured is that your request is on record in writing, with a certain date and with the amount claimed set out in detail, and that the limitation deadline starts counting again from that day.