If you landed here, a screen is probably asking for the support number on your Spanish DNI and you cannot find it. That is not your fault. The field has existed since 2006, it is printed on your card, and the label next to it has gone by three different names.
The short answer first: it is on the front, the side with the photo, and it is three letters followed by six digits. What changes with your version of the DNI is the label next to it.
What the support number is, and how it differs from the DNI number
Your DNI number identifies the person. It stays with you for life and does not change however many times you renew. Eight digits and a check letter.
The support number identifies the piece of plastic. Every renewal gets you a new card, and that card carries a new support number. This is why so many people enter theirs and get rejected: they are copying the one from their previous document, the one they had written down.
It is also why the administration asks for it. Cross-checking the DNI number against the support number confirms that the document you claim to hold is the one currently valid, not an earlier one you have since renewed.
The format never changes: three letters and six digits, like AAA000000. No spaces, no hyphens.
Where the support number is on a DNI 4.0
The DNI 4.0 is the European format, issued since 2 June 2021. You can recognise it by the EU flag with ESP inside it at the top left, and because the title “Documento Nacional de Identidad” also appears in another official language of the Union.
On this version, look for the words NUM SOPORTE on the front. The number sits directly underneath, in the data block on the right, below the expiry date.
- 1The support number, under the NUM SOPORTE label: three letters and six digits. It repeats in the small window at the top right.
- 2The DNI number: eight digits and a letter. It identifies the person, not the card, and it is not the support number.
- 3The expiry date. Every renewal means a new card, and the support number changes with it.
- 4The CAN: six digits, no letters, used for NFC chip access. It does not work as a support number.
Original schematic based on the official specimen, with sample data. PRADO record: ESP-BO-06001
Do not confuse it with the other loose number at the bottom right, six digits with no letters and no label. That is the CAN, and it exists so an NFC reader can access the chip. It is not the support number and it will not work in any form asking for one.
Where it is on a DNI 3.0, issued between 2015 and 2021
The DNI 3.0 started being issued on 2 January 2015. If your card is from those years, the label you want is NUM SOPORT, without the final E.
That is not a misprint or a regional variant. On the 3.0 the field was labelled that way, and on the 4.0 they completed the word. The number underneath has the same three-letters-and-six-digits format. Only the placement shifts a little: here it sits below the date of birth, with the expiry date beside it.
- 1The support number, under the NUM SOPORT label, below the date of birth. Same format as on the 4.0.
- 2The expiry date sits beside the support number here, not above it as on the 4.0.
- 3The DNI number, bottom left on this version.
Original schematic based on the official specimen, with sample data. PRADO record: ESP-BO-05001
This detail explains a fair number of support calls. Someone searches their 2018 card for the literal string “NUM SOPORTE”, fails to find it, and concludes their DNI does not have one.
Where it is on a Spanish electronic DNI from 2006 to 2015: the IDESP label
Here is the big one. The first electronic DNI, issued since 16 March 2006, does not mention “soporte” anywhere. Its field is called IDESP.
Same data, different name, same format. If your card is from that era and a form asks for the support number, copy whatever appears under IDESP.
- 1The support number, under the IDESP label. Same field, different name.
- 2The DNI number, bottom left.
Original schematic based on the official specimen, with sample data. PRADO record: ESP-BO-03001
The word IDESP creates a second misunderstanding worth clearing up, because it circulates widely. If you looked at the machine-readable zone on the back of a modern DNI, the first line seems to start with IDESP, and people conclude that this is the support number’s label. It is not.
- 1ID: the document type (identity document).
- 2ESP: the issuing country code. ID and ESP landing next to each other and spelling IDESP is a coincidence of the format.
- 3The support number, straight after.
- 4A check digit for the support number.
- 5The DNI number, with its letter.
That line breaks down into ID (document type) plus ESP (country code), and only then comes the support number, CAA000000 in this specimen. Then a check digit, then the DNI number. The matching letters are a coincidence of the international format.
How to tell which DNI version you have
You do not need to know version numbers. Read the printed label and work backwards.
| What your card says | Version | Issued since |
|---|---|---|
NUM SOPORTE |
DNI 4.0 | 2 June 2021 |
NUM SOPORT |
DNI 3.0 | 2 January 2015 |
IDESP |
Electronic DNI | 16 March 2006 |
If your document carries none of the three and has no chip, it predates 2006 and, unless it was issued with permanent validity, it has expired. Current validity runs in age bands: two years up to age four, five years from five to twenty-nine, ten years from thirty to sixty-nine, and permanent from seventy.
MiDNI: the support number on the mobile DNI
Since April 2026 the digital DNI has the same validity as the physical card. The data it shows is the same as the card’s, support number included.
We covered this in detail in MiDNI at check-in, so I will not repeat it here.
The support number on a Spanish passport
A frequent search with a short answer: no official reference documents a support number for the Spanish passport. The Agencia Tributaria help page that defines where the support number lives covers the DNI and the immigration documents, not the passport, and the Policía Nacional’s official description of the passport does not mention one either.
You do not really need it: each booklet carries its own passport number, which already identifies the document and changes with every renewal.
For the guest report it is even simpler: when a guest registers with a passport, the support number does not come into play at all. More on that in the last section.
The mistakes people make copying it
Almost every rejection comes from one of four places.
Mistaking zero for the letter O. In a small embossed typeface they look nearly identical. In the support number the first three positions are always letters and the next six are always digits, so if your fourth character looks like an O, it is a zero.
Copying the one from the previous card. The most common of all. It changes with every renewal.
Adding spaces or hyphens. It runs together, nine characters.
Using the CAN. Six digits, no letters, and it does something else entirely.
If the rejection reaches you from SES.HOSPEDAJES with a specific code, we have the field-by-field diagnosis in the error code guide.
If you manage accommodation: where it fits in the guest report
Three things need separating here, because half the internet runs them together and that is where most of the confusion starts.
Royal Decree 933/2021, in annex I, lists «Número de soporte del documento» among the data to collect, with no qualifier along the lines of “where applicable” or “if available”.
The SES.HOSPEDAJES web service schema, by contrast, defines the soporteDocumento field as optional, with a maximum of nine characters.
And in practice the field depends on what the guest hands you:
| Document | SES code | Support number? | Second surname? |
|---|---|---|---|
| DNI | NIF |
Yes | Yes |
| NIE | NIE |
Yes | Yes |
| NIF | NIF |
Yes | No |
| Passport | PAS |
No | No |
| Non-Spanish identity card | OTRO |
No | No |
| European document | OTRO |
No | No |
So the short answer to the question you are probably asking: no, the support number is not always mandatory. A guest travelling on a passport has no support number to give you, nothing is transmitted in that field, and the report is perfectly valid. What you cannot do is leave it empty when the guest hands you a DNI or a NIE, because that will bounce.
At RegistroViajero we require the support number only for DNI, NIE and NIF, which is where SES expects it. We are deliberately stricter than the schema: we would rather warn the guest while they are filling the form than take a rejection at eleven at night. You can see how the full check-in works if the flow interests you.
Frequently asked questions
Does the support number change when I renew my DNI? Yes, always. It identifies the physical card, not the person. Every new document brings a new one, which is exactly why so many people submit one that is no longer valid.
Is IDESP the same as the support number? Yes. IDESP is what the field was called on electronic DNIs issued between 2006 and 2015. Same data, same format, different label.
Is the support number on the back of the DNI? No, it is on the front, the side with the photo. On the back it only appears inside the machine-readable zone, as part of a longer string of characters.
Can I look up my support number without the card in front of me? The number is printed on the document, so in practice you need it to hand or a photograph you took of the front.
What if a guest has no support number? If they travel on a passport or a foreign identity card, they do not have one, and the report goes out without that field. It is only mandatory for DNI, NIE and NIF.
Does the CAN work as a support number? No. The CAN is six digits with no letters and exists so an NFC reader can access the document’s chip.
Sources
- Agencia Tributaria, Sede Electrónica, “Introduzca soporte válido”: labels and position by DNI version. Accessed 31 July 2026.
- Sede Electrónica del Catastro, “Ayuda IDESP y IXESP”: support number format. Accessed 31 July 2026.
- Policía Nacional, Ministerio del Interior, DNI 4.0 leaflet: specimen showing the CAN and the machine-readable zone, plus the launch date of the European format.
- Policía Nacional, what the Spanish passport looks like: official description of the document, with no mention of a support number. Accessed 31 July 2026.
- Council of the European Union, PRADO, records
ESP-BO-06001,ESP-BO-05001andESP-BO-03001: first issue dates and validity periods. - Royal Decree 933/2021, annex I: data to collect for the guest report.
