Juan A. Esteban

Contemporary artist and independent researcher.

Illustration of Juan Esteban’s runic monogram rendered in a three-dimensional architectural style within a frame, set against a light background.

Guides

How to prepare a certificate of authenticity for an artwork

Verified on 29 October 2026. Should any information have changed, please notify me and I shall update it with the date of the revision.

A certificate of authenticity is a dated and signed declaration that identifies a specific work and asserts a precise claim regarding it: typically, that it was created by a particular individual or that it constitutes an authorised copy of an edition. I have not identified any general requirement within Spanish regulations to provide this document for every art sale, nor is there a single legal format that all certificates must follow.

This does not render it irrelevant. When properly prepared, it connects the physical work to the artist's inventory, provides a record of the edition where applicable, and reduces ambiguity in subsequent sales, consignments, donations, and transfers. When poorly prepared, it may introduce contradictions, disclose unnecessary data, or attribute a level of authority to the document that it does not possess.

This guide is primarily intended for the artist certifying their own physical work. When another person provides the certification, or when the work belongs to an edition, incorporates digital files, or its authenticity is subject to debate, both the declaration and the evidence required to support it will change. The final template is a flexible documentary proposal, not a universal legal model.

What it certifies and which documents it does not replace

A certificate should not be limited to stating that a work 'is authentic'. It must identify the work and specify who is making the declaration and the scope thereof. Furthermore, it is inadvisable to combine functions on a single sheet that belong to distinct documents.

  • The certificate of authenticity declares the authorship or attribution of an identified work and, where appropriate, its inclusion in an edition.
  • The technical sheet describes the work for the purposes of exhibition, transport, loan, or cataloguing.
  • The master record is the internal register of the artist's archive. It contains confidential information and is not provided with the work.
  • The invoice documents an economic transaction and its tax treatment.
  • The contract establishes the price, delivery, risks, warranties, and, where applicable, authorisations regarding exploitation rights.
  • The condition report describes the material state of the work on a specific date.
  • The expert report provides a reasoned technical opinion on a matter requiring specialised knowledge.

The guide Technical sheet, certificate, and invoice: the function of each document explores these differences. The rule of thumb is straightforward: identifying data must be consistent, yet each document must retain its specific function.

Four concepts must also be distinguished:

  • Authorship: Who created the work.
  • Authenticity: Whether the piece is what it is claimed to be.
  • Attribution: Who is considered the author when the conclusion requires an assessment and uncertainty may exist.
  • Provenance: The documented sequence of ownership, custody, or circulation of the piece.

Coherent provenance may support an attribution, but it does not resolve it in isolation. A certificate signed by the artist declares authorship and identifies the specific copy; it does not automatically reconstruct the entire subsequent history. A provenance file serves this purpose, as explained in How to document the provenance of your own work.

What value it holds

The certificate is a private document. Article 326 of the Civil Procedure Law regulates the evidentiary force of private documents when their documentary authenticity is not challenged and what occurs when it is. This rule allows for the discussion of whether the document truly originates from the person appearing as the signatory; it does not render the artistic authenticity of the described piece indisputable.

If the attribution is questioned, the certificate is evaluated alongside the rest of the file: the work, signature, photographs, work process, provenance, inventory, exhibitions, invoices, correspondence, and, when technical or artistic knowledge is required, an expert opinion. Article 335 of the same law regulates the intervention of experts when specialised knowledge is required.

The Intellectual Property Act presumes the author to be the person who appears as such on the work by name, signature or sign, unless proven otherwise. The presumption in Article 6 admits proof to the contrary and does not mean that every signed piece is authentic. A certificate can reinforce documentary identification, but it does not replace examination of the object or the rest of the evidence. Nor does it prove by itself that the seller is the owner; how to check this before buying is explained in How to tell whether an artwork is stolen before you buy it.

Furthermore, it does not, by itself, certify:

  • The current ownership of the work.
  • The price paid or its market value.
  • The absence of liens or claims.
  • The state of conservation.
  • The transfer of exploitation rights.
  • The authenticity of subsequent interventions.

The declaration may acquire contractual relevance. If authorship was a decisive condition of the purchase, an inaccurate statement may affect the consent or the agreed warranties. Article 1266 of the Civil Code regulates error regarding the substance of the thing or conditions that primarily motivated the contract. The concrete consequence depends on the facts, the contract, and the available evidence.

Who may issue it

The artist

During their lifetime, the artist is the only person who can declare, at first hand, the authorship and the relationship of a piece to their inventory or an edition. They must sign with their full name and identify a professional contact channel. If working through a gallery, they should not provide pre-signed, blank certificates.

Heirs, archives, or designated individuals

After the artist's death, the authority of the certifier no longer derives from having created the work, but from their knowledge of the corpus, the archive they curate, and the available documentation. Article 15 of the Intellectual Property Law regulates who may exercise certain moral rights after death, but it does not, by itself, create a general authorisation to authenticate pieces.

Anyone issuing a posthumous document must indicate:

  • The capacity in which they are acting.
  • Which object was examined.
  • Which documentation was consulted.
  • What comparison was performed.
  • Whether they are formulating a conclusion of authenticity, an attribution, or merely an inclusion in an archive.
  • The limitations of their declaration.

Galleries

A gallery may document a sale, a consignment, and the provenance within its own commercial relationship. This does not equate to speaking on behalf of the artist. The Codi de relacions entre l’artista visual i la galeria d’art hosted by PAAC recommends that certificates be signed by the artist and that representation does not authorise the gallery to issue them independently. This is a professional reference, not a generally applicable legal rule.

Committees, foundations, and specialists

They may issue opinions or attribution documents provided they possess sufficient knowledge and sources. Their authority depends upon their competence, independence, methodology, access to the archive, and the clarity of their conclusion. A refusal to certify does not automatically equate to a judicial declaration of falsehood.

I have not identified a Spanish public authority that certifies the authenticity of works of art in a general capacity. The Intellectual Property Registry, where registration is appropriate, serves a different function and does not replace the certificate for a specific piece.

Content requirements

There is no single legal list. As a matter of documentary practice, the certificate should include:

  1. Certificate number. A unique code, taken from a register and never reused.
  2. Inventory identifier. The same one that appears in the master record.
  3. Authorship. The artist's full name or the precise attribution formula.
  4. Title. The current title and, if useful, documented previous titles.
  5. Date of the work. The year of completion and, where it provides information, the period of creation.
  6. Technique, materials, and support. A concrete description, not a generic formula such as "mixed media" without breakdown.
  7. Dimensions. Height, width, and depth, in a fixed unit and indicating whether they include a frame, plinth, or other elements.
  8. Reference images. Front, back, signature, inscriptions, and identifying details.
  9. Signatures, labels, and marks. Transcription and location.
  10. Condition of the object. Unique work, edition copy, proof, reproduction, or other category described without ambiguity.
  11. Edition details. Copy number, declared print run, and existing proofs, where applicable.
  12. Declaration. What exactly the signatory affirms.
  13. Scope and limitations. What the document does not certify and which subsequent changes remain excluded.
  14. Place and date of issue. Distinct from the date of the work's creation.
  15. Signature and identification of the certifier. And, if not the artist, the capacity in which they act.
  16. Annexes. Instructions, components, or files when the work requires them.

A title alone does not identify a work. It may be repeated, changed, or written in various ways. Identification must arise from a coherent set of inventory, images, measurements, technique, marks, and components. The inventory number of the master record must not be reused even if the piece is lost or destroyed.

Do not write codes directly onto any support. For fragile or sensitive materials, consult conservation and link the identifier through documentation, photographs, appropriate labels, and packaging.

Data to exclude

The certificate may circulate for decades and pass to individuals who were not involved in the initial transaction. It should not become a copy of the commercial file.

It is advisable to keep the following out:

  • Price, discounts, and insurance value.
  • Invoice number and date, unless a strictly necessary reference.
  • Buyer's personal data.
  • Current location of the work.
  • Commissions and payment terms.
  • Commercial correspondence.
  • Sketches and working files not intended for circulation.
  • Internal notes or research queries.

The principle of minimisation under Article 5.1.c of the GDPR requires that personal data processed be adequate, relevant, and limited to what is necessary. Therefore, as a documentary criterion, it is preferable to certify the work and register separately to whom the document was delivered.

In the internal archive, it is advisable to retain:

  • Copy of the issued certificate.
  • Identity of the recipient.
  • Date and reason for issue.
  • Relationship with invoice and contract.
  • Photographs used.
  • History of duplicates, replacements, and cancellations.
  • Evidence of process and provenance.
  • Verified backups.

I have not identified a specific legal retention period applicable to all certificates of authenticity. From the perspective of the artist's archive, it makes sense to maintain the file as long as the work may circulate and there is an interest in verifying its identity and authorship.

Editions, copies, and reproductions

When there are multiple copies, the certificate must identify both the individual unit and the set to which it belongs. The print run must be defined before marketing the edition and kept consistent across all documents.

Indicate:

  • Copy number.
  • Total number of the edition.
  • Number and nature of proofs, if any.
  • Production technique.
  • Involvement of the artist and third parties.
  • Existence of other distinct editions.
  • Elements or files that are not part of the edition.

Professional terminology is not entirely uniform. An "artist's proof" is usually marked distinctly and declared separately from the numbered print run, but the important factor is that the number of proofs and their relationship to the edition remain fixed without concealment. Do not expand an edition after selling it as closed.

The VAT Act includes numerical limits for certain categories for tax purposes, including engravings, prints, lithographs, sculptures, tapestries, enamels, and photographs. These are fiscal definitions, not universal rules of creation, authenticity, or best practice. Do not determine an edition size solely to fit a tax classification without appropriate professional advice.

For the purposes of this guide, the following labels are used in an operational sense:

  • Unique work: A piece with no declared equivalent copies.
  • Edition copy: An authorised and identified unit within a print run.
  • Proof: A distinct copy whose existence and function are declared.
  • Copy: An object that reproduces the work and is not presented as a unique work or as a copy from the described edition.
  • Reproduction: An image or replica intended for documentation, dissemination, or any use other than sale as an original or authorised copy.

These formulas do not replace the legal definitions that may apply in litigation, taxation, or contract law. The decisive factor is to describe exactly what is being delivered and not to present a reproduction as an original.

Digital, variable, or installation-based work

For a digital work, it is insufficient to print a sheet and associate it with an imprecise file. The certificate must identify:

  • Name and version of the files.
  • Formats.
  • Checksums where useful.
  • Copy number and edition size.
  • Delivered media.
  • Physical components.
  • Technical dependencies.
  • Rules for preservation, migration, or replacement.
  • Versions that do not form part of the edition.
  • Exhibition, execution, or adaptation permissions, where applicable.

The guide How to certify a digital work and its editions explores these scenarios. A token may record a transaction, but it does not, in itself, demonstrate authorship, authenticity, integrity, or the scope of the rights transferred.

For installation-based, conceptual, or variable works, the certificate may refer to artist instructions and documentation. The Metropolitan Museum templates for time-based works are documentation and conservation questionnaires, not certificates. They serve as a reference for the type of information that may be missing if the entire work is reduced to a declaration of authenticity.

When the certificate incorporates installation conditions or execution permissions, it must distinguish between:

  • The retrospective declaration of what the work is.
  • The instructions for its realisation or preservation.
  • The contractual authorisations to exhibit, reproduce, or adapt it.

Peter J. Karol’s article on “permissive” certificates examines this combination under US law. It is cited as a contrast, not as a rule automatically applicable in Spain.

Delivery, archiving, and incidents

To the buyer or recipient, deliver:

  • The signed certificate.
  • The necessary reference images.
  • The technical sheet consistent with the certificate.
  • The invoice and the contract as separate documents.
  • Installation, preservation, or assembly instructions, if they exist.
  • A clarification regarding exploitation rights, preferably developed in the contract.

The purchase of the physical medium does not, in itself, transfer exploitation rights. Article 56 of the Intellectual Property Act establishes this separation and recognises, within its limits, the right of public exhibition held by the owner of the original of a visual or photographic work. Selling a painting is not selling its rights explains the practical consequences.

Do not deliver the master sheet, the confidential data sheet, or source files that are not part of the transaction.

Loss

Do not issue a copy indistinguishable from the lost original. Verify the work and issue a document marked as a duplicate, with a reference to the previous number and date. Record the incident.

Error

Do not correct an already issued certificate by hand. Create another that identifies the replaced document and mark the previous one as cancelled in the register. Do not destroy the documentary trail.

Restoration or modification

The certificate describes the work at the date of issue. Interventions must be recorded in the master sheet and the condition report. If they substantially modify the identification or configuration of the work, it may be necessary to issue an update explaining the relationship with the previous certificate.

The author's right to demand respect for the integrity of the work is recognised in Article 14 of the Intellectual Property Law. Its concrete application to an intervention requires an analysis of the alteration, the prejudice, and the circumstances of the case.

Destruction or loss of the work

Mark the inventory and the certificate as withdrawn. Do not reuse their numbers. The record retains historical value even if the object no longer exists.

Disputed authenticity

Do not alter the piece or replace documents. Preserve the certificate, photographs, provenance, contract, and communications. Obtain an independent assessment with specific expertise and record its method and scope. A contrary opinion does not, in itself, equate to a finding of forgery or demonstrate fraud. Avoid public accusations without a sufficient basis. The article Neither authentic nor false examines a case in which neither the expert authority nor the technical analysis definitively settled the attribution.

Annotated template

CERTIFICADO DE AUTENTICIDAD N.º [código único]
Hoja [n] de [total]

Autor o autora: [nombre y apellidos]
Título: [título vigente] ([títulos anteriores documentados, si existen])
Número de inventario: [código]
Año de la obra: [año de terminación o intervalo]
Técnica, materiales y soporte: [descripción concreta]
Medidas: [alto × ancho × fondo, sin marco, en centímetros]
Condición: [obra única / ejemplar n.º X de una edición de Y /
prueba n.º X de Z / copia / reproducción / otra]
Firma e inscripciones: [ubicación y transcripción]
Imágenes de referencia: [relación de imágenes incorporadas o anexas]

Declaración:
Yo, [nombre y apellidos], declaro que la obra identificada en este
certificado es obra de mi autoría [o: es el ejemplar n.º X de la edición
descrita, realizado por mí o bajo mi autoridad].

Este certificado se refiere únicamente a la obra identificada y a su
configuración en la fecha de emisión. No acredita por sí solo la propiedad
ni el valor de la obra y no transmite derechos de explotación. No cubre
intervenciones o modificaciones posteriores.

Documento: [original / duplicado del certificado n.º ___, emitido el ___ /
sustituye al certificado n.º ___]

Lugar y fecha de emisión: [lugar], [fecha]
Firma: [firma]
Nombre y contacto profesional: [nombre, correo o web]

Adapt the declaration when the artist is not the signatory. In such instances, one must formulate an attribution, identify the authority of the signatory, and describe the object, sources, and methods examined. For a digital or variable work, append files, versions, integrity, dependencies, and substitution rules in an annex.

Checklist

  • The work is identified by inventory, title, date, technique, support, dimensions, and images.
  • The data correspond with the master record, the technical sheet, the invoice, and the contract.
  • The condition of the piece is unambiguous.
  • The edition, the copy number, and the proofs are declared where applicable.
  • The declaration asserts only that which the signatory can substantiate.
  • The identity and status of the certifier are clearly stated.
  • The document includes the place, date of issue, signature, and a unique number.
  • It does not incorporate unnecessary personal or financial data.
  • It does not conflate the transfer of the physical support with the assignment of rights.
  • A copy is retained, and the recipient is recorded in the archive.
  • Duplicates, replacements, and cancellations refer to the previous document.
  • Backups have been verified.

Itinerary

An open conversation

This guide describes a documentary practice, not a closed legal regime. The cited regulations govern specific aspects: authorship, moral rights, the separation between support and rights, documentary evidence, contractual consent, data protection, and fiscal definitions. The recommended content, the separation of reserved data, the handling of duplicates, and the template are my own editorial criteria and are presented as such.

If you work in a gallery, an artist's archive, conservation, valuation, or art law and detect an error or a scenario that requires clarification, you may write to me.

Sources

Regulations

Professional and academic references

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