A digital certificate with a NIE, Cl@ve and letting your adviser act for you

Almost everything a foreigner does with the Spanish administration now begins with a login: filing a return, downloading a tax certificate, opening the letter that waits in an electronic mailbox. The NIE is the number; it is not the key. There are three keys, a digital certificate, Cl@ve and, for citizens of the European Union, the electronic identity of their own country, and each has its own way in for someone who is not Spanish. The fourth thing to settle is how your adviser acts for you, and the law's answer never needs your key: it gives an adviser two ways to act in your name with a key of their own. This note takes them in that order and ends with a table of what each agency asks for.

The certificate is free, and a NIE is enough

The certificate this note deals with is the one issued by the FNMT, the State mint, and its own page says who can have one: Cualquier ciudadano español o extranjero, mayor de edad o menor emancipado que esté en posesión de su DNI o NIE, podrá solicitar y obtener su certificado digital de forma gratuita, any Spanish or foreign citizen, of age or an emancipated minor, who holds a DNI or a NIE may request and obtain the digital certificate free of charge. The page lists four ways of getting it. For the holder of a NIE every one that is open today passes through an office. Identification by video is closed: for that route Será necesario el DNI electrónico vigente, a valid electronic DNI will be necessary, and the FNMT's mobile app says the same of its own video option, which for now accepts only a valid DNI.

The request is made on the FNMT's website or in its app, a request code arrives by e-mail, and you take the code and your papers to an accreditation office; the certificate is downloaded afterwards. A citizen of the European Union shows the document that carries the NIE, which may be the foreigner's identity document, the certificate of registration as a Union citizen or the official paper that granted the number, together with the passport or the identity card of the home country. Any other foreigner shows the foreigner's identity card that carries the NIE, or the official paper that granted it, together with the passport. Of that official paper the FNMT says it serves to check that you hold a NIE whether or not the paper itself is still in date; the passport or identity card has to be valid and the original, or an officially certified copy.

The FNMT counts more than 2,400 accreditation offices in Spain, and those of the tax agency and of the Social Security work by appointment. The post office is not one of them: Este certificado NO puede solicitarse a través de las oficinas de Correos, this certificate cannot be requested through post offices. From abroad the route is a consulate, and the FNMT's wording is precise, las Oficinas Consulares de carrera de España en el extranjero, the career consular offices of Spain abroad; it publishes the list of those that do it. If you cannot go yourself, someone else may go for you, but a power of attorney will not do: se le exigirá la previa legitimación de tu firma del contrato ante notario, that person will be asked for your signature on the contract, legitimated beforehand by a notary. And a person holds one FNMT certificate at a time: asking for a new one in the app revokes the old one, and the same certificate can be installed on a computer and on a phone from its backup copy.

A company needs a certificate of its own

For a company the FNMT issues three certificates of representation, and it tells applicants which is theirs. The sole administrator of an SA or an SL, or one of several administrators who can each act alone, asks for the administrator's certificate, and only online: Este certificado sólo puede obtenerse de forma On Line con un certificado de Persona Física de la FNMT-RCM o DNI electrónico, this certificate can only be obtained online with an FNMT certificate of a natural person or an electronic DNI. A foreign administrator therefore gets the personal certificate first, with the NIE, and that NIE has to be the one recorded with the appointment at the Registro Mercantil, the companies register. The administrator's certificate costs 24 euros before taxes and lasts two years. Other representatives of a company, such as administrators who must sign together, an attorney or a company that administers another, take the certificate of representative of a legal person: 14 euros before taxes, two years, and the papers of the Registro Mercantil that the FNMT lists.

The Supreme Court has said what the administrator's certificate is worth. In judgment 1179/2021 of 28 September 2021, on the sole administrator of a sociedad anónima, it held that the administrator represents the company by law and that one who holds the certificate no necesita aportar, mientras esté vigente dicho certificado, un poder de representación de la sociedad con motivo de cada actuación concreta ante la Administración, does not need to produce, while that certificate is in force, a power of representation of the company for each particular step before the Administration.

Cl@ve, the lighter key

Cl@ve is the identification system the administrations share, and it is for natural persons: a registration, a mobile phone, and the app or a code by text message each time you sign in. It asks for less than the certificate, and at the tax agency it opens the online procedures for individuals wherever the rules do not demand an advanced signature. Registration is where a foreigner has to read carefully. The newest route, video identification in the Cl@ve app, is closed to NIE holders for now: Temporalmente solo se ofrecerá el registro por videoidentificación a ciudadanos españoles con un DNI en vigor, for the time being registration by video identification will only be offered to Spanish citizens with a valid DNI. Three routes remain.

The first is a letter. You ask for it online with the NIE and the support number of your document, and the tax agency posts an invitation letter al domicilio fiscal que conste en nuestras bases de datos en ese momento, to the tax address held in its databases at that moment. Check which address that is before you ask, because that is where the letter goes, and you have 60 days to use it. Its code, a mobile number, which may be a foreign one with the country prefix, and an e-mail address complete the registration. The second route is the certificate: whoever already holds one registers in Cl@ve online. The third is a desk. The tax agency's offices register people by appointment and other bodies have registration offices of their own; a foreigner brings the NIE, the passport, a mobile number and an e-mail address, and has to go in person: Este trámite no puede efectuarse mediante representación ni a través de apoderamiento, this step cannot be carried out through a representative or by power of attorney.

The letter gives the basic level of registration; the certificate and the desk give the advanced one, which some bodies other than the tax agency may require for their most common procedures. Someone who lives abroad and holds nothing but the paper that granted the NIE should look at the certificate first: the Cl@ve form asks for a support number that the agency's help locates on the foreigner's card, the residence permit or the Union citizen's certificate, while the FNMT accepts that paper with the passport.

Whichever way you register, the codes are yours alone. The tax agency describes Cl@ve as de uso personal, directo e intransferible, for personal, direct and non-transferable use, and counts as misuse acceder a servicios electrónicos en nombre del ciudadano utilizando sus credenciales o factores de autenticación, incluso con su consentimiento, accessing electronic services in the citizen's name using the citizen's credentials or authentication factors, even with the citizen's consent. An adviser who asks for your code over the phone in order to file your return is asking for exactly that.

A European identity can open the same door

Citizens of another State of the European Union have a third key that needs no Spanish office: the electronic identity their own country gave them. The tax agency accepts it, through the European eIDAS system, for some of the main procedures in a list of areas that it says it will keep extending, among them income tax and non-resident income tax, corporate tax, VAT, debts, customs and, the one that matters most for this note, powers. There is one condition, and it is a Spanish number: necesitas primero tener uno de estos identificadores españoles, you first need to have one of these Spanish identifiers, which are a DNI, a NIE or a tax number beginning with L or M. With the NIE in hand, the option appears in the sign-in menu of each procedure that accepts it.

Two ways the law gives your adviser

The law gives an adviser two ways to act in your name, and neither needs your key. A Cl@ve code used by someone else is, as the tax agency puts it, misuse of the system. Our advice is the same for the certificate file and its password: do not hand them over. Whatever is signed with them is signed as you, before every administration that accepts the certificate, and the two routes below make it unnecessary.

The first is called social collaboration. The General Tax Act lets the tax administration sign agreements with the professional bodies and associations of tax advisers (Ley 58/2003, article 92), each member joins by signing an individual document of adherence (Real Decreto 1065/2007, article 79), and one of the things the agreement covers is the filing of returns and other tax documents previa autorización de los obligados tributarios, with the prior authorisation of the taxpayers. The adviser files with their own certificate; you sign an authorisation, for which the tax agency publishes models, and keep a copy. The limits are the tax agency's own words. The representation is the one needed for las acciones de carácter mecánico, adjetivo y burocrático tendentes a la presentación de esa documentación por Internet, the mechanical, accessory and bureaucratic acts that lead to filing that documentation online. It does not make the adviser your representative for anything else and gives no right to receive the agency's communications, even those that follow from the document filed. And the agency podrá requerir, en cualquier momento, la acreditación de dicha representación, may require proof of that representation at any moment (Ley 58/2003, article 46), which is why the signed paper has to exist before the return goes in. The agency also warns advisers that every query made for a client leaves a record of what was consulted and of whose identification was used.

The second rests on the Act's general rule that a taxpayer may act through a representative que podrá ser un asesor fiscal, con el que se entenderán las sucesivas actuaciones administrativas, who may be a tax adviser, with whom the successive administrative steps will be conducted (article 46). The tax agency keeps a register of powers for it, the registro de apoderamientos. You grant a power to a person or a company, and from then on the attorney acts for you con su propio certificado electrónico de usuario, with their own electronic user certificate. You choose how far the power goes: procedure by procedure, or by any of four general categories, which are the procedures for which the Act demands proof of representation (appeals, waivers of rights, refund claims and the other steps that need your signature), the consultation of your personal data, the reception of notifications, and the payment of debts by direct debit from accounts in your own name. It can be granted online with an electronic signature the agency accepts, in person at one of the agency's offices on the form it approved, or by a public deed, or a private document with a notarised signature, that follows that form (Resolution of 18 May 2010, as amended on 9 March 2018).

A registered power has a term. Los poderes inscritos en el registro tendrán una validez determinada máxima de cinco años a contar desde la fecha de inscripción, powers entered in the register shall have a fixed validity of at most five years from the date of entry (Ley 39/2015, article 6), and the tax agency lets a power be extended in the two months before it lapses. One date under that rule has already passed: powers registered before 2 April 2021 that nobody extended perderán su efectividad el día 2 de abril de 2026, would lose their effect on 2 April 2026. The Canary Tax Agency, whose older powers were open-ended, published the same warning for its own register. Anyone who gave an adviser a power years ago and has renewed nothing since should assume it is gone, and look. You can withdraw a power whenever you like, and the withdrawal takes effect when the agency is told of it. The agency's own advice to anyone who fears their codes were misused is to review the powers in force in their name and revoke those they do not recognise.

One register for each agency

The administrative procedure Act has every administration keep an electronic register of powers and lets each body keep one of its own. It distinguishes a general power for any step before any administration, a power for one administration or body, and a power for named procedures (Ley 39/2015, article 6). For taxes and Social Security, a client in Fuerteventura deals with three registers and one separate system.

The Canary agency's general powers follow the State's first three categories, which are the procedures that need proof, data and certificates, and notifications; the specific procedures are listed in its Resolution of 10 January 2023, and it runs its own scheme for advisers who file for clients. The Social Security's register is governed by Orden ISM/189/2021. A power is granted there online with a certificate or Cl@ve, and people who have neither can grant it in person at its provincial offices; companies and others obliged to deal with it electronically cannot. Its own published guide says that a general power entered in the State administration's register need not be repeated, because the two registers are connected. The RED system is a different thing from a power: it is where an employer or a self-employed worker confirms, and can later withdraw, the adviser's access to their contribution accounts.

Where the letters go

Filing and receiving are two different rights. An adviser who only files under social collaboration receives nothing. A power for notifications is what lets the adviser receive the agency's letters in an electronic mailbox, under the ten-day rule we explained in our note on electronic notifications. It is a power the attorney has to accept before it works: the Canary agency and the Social Security say so expressly, and the State agency's page on extensions assumes it.

There is a third situation: a procedure already open, in which your representative has told the agency in writing where to notify. The Supreme Court ruled on it in judgment 902/2025 of 1 July 2025. The Spanish branch of a foreign company, obliged to receive its notifications electronically, had named its lawyers' office for the notification of a penalty; the agency left the penalty in the company's electronic mailbox, the ten days passed and the claim against it was filed out of time. The court set the 20,000-euro penalty aside and fixed as doctrine that la Administración tributaria deberá practicar las notificaciones por el cauce que sea procedente u obligatorio, en el domicilio expresamente designado por el contribuyente o su representante legal, the tax administration must make notifications by the channel that is appropriate or obligatory, at the address expressly designated by the taxpayer or the taxpayer's legal representative. A second appeal on a neighbouring question, whether an attempt at the tax address is enough when the taxpayer had given another one, was admitted on 3 December 2025, and we found no judgment in it on 6 October 2026. The prudent reading is the modest one: name the address in writing in each procedure, and do not count on a court to rescue a letter that nobody opened.

What a power does not change

Three things stay where they were. The tax and its deadlines stay yours: Las actuaciones tributarias realizadas con el representante del obligado tributario se entenderán efectuadas directamente con este último, tax proceedings carried out with the taxpayer's representative shall be deemed carried out directly with the taxpayer (Real Decreto 1065/2007, article 112), so a return your adviser files late is your late return, with the surcharges set out in our note on late filing. The adviser's liability does not grow because the power is registered; the tax agency says so on its own page. And a power in the register is not the representative that a non-resident sometimes has to appoint: those who do not live in Spain deberán designar un representante cuando lo establezca expresamente la normativa tributaria, must designate a representative when the tax rules expressly say so (Ley 58/2003, article 47), a separate figure with its own form, explained in the sister piece at Fuerteventura Properties on the tax representative of owners abroad.

What our advisory does

Our Caleta de Fuste and Costa Calma offices handle personal income tax and non-resident tax for individuals, and the NIE paperwork that every route in this note starts from; for businesses, the tax desk represents the client before both tax agencies. What we do for individuals is on our advisory page and the work for businesses on tax advisory. You can book a consultation and bring your NIE document and your passport.

Common questions

I live abroad and all I have is the paper that gave me my NIE. Can I get the certificate?

Yes. The FNMT accepts the official paper that granted the NIE, whether or not the paper itself is still in date, together with a valid passport or, for citizens of the Union, the identity card of their country. You make the request online and prove your identity in person, at an accreditation office in Spain or at one of the Spanish career consulates on the FNMT's list. Video identification is not available to NIE holders today.

Can my adviser register me in Cl@ve, or collect my certificate for me?

Not Cl@ve: registration at a desk has to be done in person and cannot be done through a representative or by power of attorney, and the invitation letter goes to your own tax address. For the certificate a third person may go to the office in your place only if a notary has legitimated your signature on the contract. In both cases the key that results is yours and stays with you.

My adviser files my returns. Does the adviser also receive the tax office's letters?

Not for that reason alone. Filing under social collaboration covers the act of filing and nothing else, and the tax agency says it gives no right to receive its communications. Letters reach the adviser only if you grant a power for notifications in the register and the adviser accepts it. Without that they come to you, on paper or in your own electronic mailbox.

I gave my adviser a power at the tax agency years ago. Is it still valid?

If it was registered before 2 April 2021 and nobody extended it, it lost its effect on 2 April 2026. Powers registered since then carry a term of at most five years and can be extended in the two months before they end. The tax agency's electronic office shows the powers in force in your name, and a new one can be granted there.

I am the sole administrator of an SL and I am not Spanish. What do I need?

First your own FNMT certificate, obtained with the NIE. With it you request the administrator's certificate online: 24 euros before taxes, valid for two years, provided your NIE is the one recorded with your appointment at the Registro Mercantil. The Supreme Court has held that, while that certificate is in force, the administrator need not produce a power from the company for each step before the Administration.

Facts verified in October 2026 (Ley 58/2003, General Tributaria, articles 46, 47 and 92; Real Decreto 1065/2007, articles 79 and 112; Ley 39/2015, article 6; Orden ISM/189/2021, articles 5, 8 and 9 and its first additional provision; the pages of the FNMT on its certificates, of the State Tax Agency on Cl@ve, eIDAS, its register of powers and social collaboration, of the Canary Tax Agency on its register of powers and of the Social Security on its register and the RED system, all as they stood on 6 October 2026; Supreme Court, judgments 1179/2021 of 28 September 2021 and 902/2025 of 1 July 2025, and its order of 3 December 2025 in appeal 7909/2024). This is general information, not advice on a particular case.