Reviewed as of 27 September 2026. If anything has changed, let me know and I will update it with the date of the change.
When a work is sold or leaves the studio, it is typically accompanied by a technical data sheet, a certificate of authenticity and, if the transaction is subject to invoicing, an invoice. These are not three versions of the same document. Each serves a distinct purpose, and none replaces the others.
This guide distinguishes their uses and proposes a coherent identification system. It is not legal or tax advice.
The technical data sheet describes the work
The technical data sheet records the details required to identify the piece: inventory number, title, date, technique, materials, support, dimensions and, where applicable, duration, components, edition and copy number.
It is used for exhibitions, loans, catalogues, applications and archives. It may include instructions for installation, conservation or reproduction if the work requires them.
What it does not demonstrate. A data sheet does not, in itself, verify authorship, ownership or a transfer. Its value depends on the accuracy of the data, its link to the piece and its consistency with the inventory and other documentation.
The certificate contains a declaration of authenticity
The certificate is the document in which the artist, their successors in title, or a person or entity with sufficient authority declares the authenticity or attribution of a work. In Spain, there is no general legal format or ordinary public registry that renders any certificate definitive.
For a contemporary work issued by the artist themselves, you should include:
- the artist's name and professional contact details;
- inventory number;
- title, date, technique, materials, support and dimensions;
- a photograph sufficient to identify the piece;
- edition, copy number and total print run, if applicable;
- a precise declaration of authorship;
- place and date of issue;
- signature and certificate number.
Keep a copy and record to whom it was delivered. For digital, installation or variable works, include the components, files, versions and instructions that define what constitutes the work.
What it does not demonstrate. It is not a valuation, it does not guarantee a price, it does not transfer ownership, nor does it assign exploitation rights. Its evidentiary and commercial force depends on who issues it, what it affirms and the documentation supporting it.
The invoice documents a transaction
The invoice is a tax document. It identifies the issuer and the recipient, the transaction, the date, the consideration and the applicable taxes or mentions. Its mandatory content depends on the type of invoice and the transaction.
The Billing Regulations remain those approved by Royal Decree 1619/2012, amended in 2026, among other regulations, by Royal Decree 238/2026 on electronic invoicing between entrepreneurs and professionals. To determine the format and mentions required for a specific sale, consult the specific invoicing guide or a professional.
Include the title, year, technique, dimensions and inventory number in the description. This allows the transaction to be linked to the work without ambiguity.
What it does not demonstrate. The invoice proves the transaction it documents, but it does not, in itself, make a work authentic. Nor does it transfer copyright unless there is a written assignment identifying such rights. Ownership of the physical support and exploitation rights are independent.
A common identifier
The most frequent error is discrepancy between documents: a different title, incompatible dimensions or different dates. The solution is to assign a unique identifier to each work and copy the data from a master record.
The master artwork record: annotated template explains the system and offers a complete workbook in ODS format, in addition to CSV exports of the general record, the restricted data and the gallery deposit.
Use the master record as a common source. The technical data sheet, the certificate and the invoice description must repeat the same inventory number, title, date, technique and dimensions. Each document will subsequently add information specific to its function.
The identifier must accompany the piece, but it should not be inscribed directly onto any material. For delicate supports, consult conservation and use labels, packaging and photographs linked to the same code.
What to provide
- Exhibition: technical data sheet and, if applicable, installation instructions and credit.
- Loan: technical data sheet, condition report, photographs and handling conditions.
- Sale: invoice when there is an obligation to issue one; certificate when agreed upon or where it is standard practice; technical data sheet or identification document for the work.
- Edition: in addition, copy number, total print run, artist's proofs if they exist, and rules for the replacement or destruction of matrices and files when relevant.
Do not assert that an invoice or certificate is always mandatory for every delivery without analysing the transaction. The tax obligation depends on who is selling, to whom and under what conditions; the certificate generally responds to contractual and market practice.
On the open conversation
This guide distinguishes three documents that frequently accompany a work. The content of the invoice derives from tax regulations; the data sheet and the certificate rely primarily on the sector's documentary practice. If you work in a gallery, artist's archive, conservation or valuation and identify a point that requires clarification, the guide remains open.