Several rules apply in Spain for the numbering of invoices ("factura") and simplified invoices ("factura simplificada"). Furthermore, the Spanish Ministry of Finance provides recommendations for the numbering of invoices.

Royal Decree 16/2012 on the obligation to issue invoices defines the contents of invoices and simplified invoices. The term "cash receipt," used in Austria and other countries, is synonymous with the simplified invoice ("factura simplificada") in Spain.

Invoice number

In addition to other mandatory elements, each invoice must have a number and, if applicable, a series.

• The numbering of the individual invoices must be continuous within the series (monotonically increasing).

Invoice series

Invoice series can be used for specific purposes, for example, if the company has several branches, as an identifier for each location.

However, under certain circumstances, the use of separate invoice series is mandatory. Separate invoice series must be used in the following cases:

• if some invoices are not issued by the performing company but by the recipient.
• when correcting invoices
  
  Note: Returning goods and services is not a corrective measure! Corrections are changes to the original invoice due to errors (e.g., incorrect VAT). Corrected invoices must include a reference to the original invoice.
• when issuing Invoices and simplified invoices
• invoices issued by successful tenderer as a result of administrative and judicial enforcement proceedings.
• invoices issued to document delivery of mobile phones, video game consoles, laptops and digital tablets; as well as silver, platinum and palladium, in unwrought, powdered or semi-manufactured form, when these give rise to the reversal of the taxable person.
• invoices of travel agencies acting as intermediary
• invoices to document intra-group transactions carried out between entities that opt for the advanced level of the Special Regime for the group of entities

As described above, invoices and simplified invoices should be managed in separate invoice series (number ranges). See examples below.

AEAT recommendations

The "Agencia Estatal de Administración Tributaria" (AEAT - Spanish Tax Administration Agency) provides recommendations on its website for invoice numbering and the use of series.

• Recommended character set: 0123456789ABCDEFEGHJKLMNPQRSTUVXYZ. Lowercase letters are not recommended.
• Spaces: If used, only one character is used, never more than one.
• Special characters: hyphen “-”, underscore “_”, slash “/”, period “.”
• Invoice Series: should be used as a prefix, followed by the invoice number with a space (or separator) in between.
• The invoice number must not begin with a space (i.e. left-wrapping text).

Examples of invoice numbers including series

The following examples of invoice numbers and series are for illustrative purposes only. You can create your own number series based on the AEAT regulations and recommendations.

Invoices

• are maintained in a separate number range (or several, if necessary - see above).
• It is recommended to start with "0" or "1," but this is not mandatory. The numbering can also begin with "4711," for example, as long as the subsequent numbers are continuous and ascending (4711, 4712, 4713,...).
• Additionally, an indicator (prefix) for the series should be specified, e.g., "FA" or "FAC" for "invoice" ("factura")

Examples of invoice series:

• FAC25-0001, FAC25-0002, FAC25-0003,..., FAC25-000n   (Prefix: FAC25 for "Invoice 2025")
• FA2025 0001, FA2025 0002, FA2025 0003,...,FA2025 000n  (Prefix: FA2025 for "Invoice 2025")

Simplified invoices

• are maintained in a separate number range (or several, if necessary - see above).
• It is recommended to start with "0" or "1," but this is not mandatory. The numbering can also begin with "4711," for example, as long as the subsequent numbers are continuous and ascending (4711, 4712, 4713,...).
• Additionally, an indicator (prefix) for the series should be specified, e.g., "FS" for "Simplified Invoice" ("factura simplificada")

Examples of simplified invoice series:

• FS25-0001, FS25-0002, FS25-0003,..., FS25-000n   (Prefix: FS25 for "Simplified Invoice 2025")
• S2025 0001, S2025 0002, S2025 0003,...,S2025 000n  (Prefix: S2025 for "Simplified Invoice 2025")

Correction invoices

As mentioned above, correction invoices are NOT used in the case of goods exchanges, returns or similar, but to correct errors in the respective original invoice.

• are maintained in a separate numbering range (or several, if necessary - see above).
• It is recommended to start with "0" or "1," but this is not mandatory. The numbering can also begin with "4711," for example, as long as the subsequent numbers are continuous and ascending (4711, 4712, 4713,...).
• Additionally, an indicator (prefix) for the series should be specified, e.g., "REC" for "correction invoice" ("factura rectificativa")

Examples of series corrective invoices:

• REC25-0001, REC25-0002, REC25-0003,..., REC25-000n   (Prefix: REC25 for "Correction Invoice 2025")
• R2025 0001, R2025 0002, R2025 0003,...,R2025 000n  (Prefix: S2025 for "Correction Invoice 2025")

Sources

• Real Decreto 1619/2012, de 30 de noviembre, por el que se aprueba el Reglamento por el que se regulan las obligaciones de facturación ("Royal Decree 1619/2012 of 30 November approving the Regulation on Invoicing Obligations")
• Website of AEAT (Agencia Tributaria)