Spanish DNI Support Number: Where to Find It

The form says the support number is not valid and says nothing else. The field it is rejecting is printed on the card in front of you, under a label that looks nothing like the words being asked for. Third attempt, the screen locks, and the DNI takes the blame.

It is not your fault and it is not the document’s. The field has existed since 2006 and has been printed ever since, but the label above it has changed three times, and nothing tells you which one applies to the year your card was issued.

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 AAA000000¹. 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 2021². 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 date³.

Do not confuse it with the other loose number at the bottom right, six digits with no letters and no label². 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 the support number is on a DNI 3.0 (2015-2021)

The DNI 3.0 started being issued on 2 January 2015⁴. If your card is from those years, the label you want is NUM SOPORT, without the final E³.

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.

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.

The support number on an electronic DNI from 2006 to 2015: IDESP

Here is the big one. The first electronic DNI, issued since 16 March 2006⁴, does not mention “soporte” anywhere. Its field is called IDESP³.

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.

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.

That line breaks down into ID (document type) plus ESP (country code), and only then comes the support number, CAA000000 in this specimen². 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.

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 seventy⁴.

MiDNI: the support number on the mobile DNI

The digital DNI carries the same legal effect as the physical card for identification, and since April 2026 you cannot refuse it. The data it shows is the same as the card’s, support number included.

We cover it in detail in MiDNI at check-in.

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 passport³, and the Policía Nacional’s official description of the passport does not mention one either⁵.

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 the support number

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 digits¹, 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.

Is the support number mandatory 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”⁶.

The SES.HOSPEDAJES web service specification, which the Ministry hands to whoever registers and does not publish on its sede electrónica, does condition it. In its section 3.1.1.1, the one covering the filing of guest reports, it defines soporteDocumento as a string of up to nine characters and marks it mandatory when the document type is NIF or NIE⁷. That is the rule the system applies when it receives the report, and it is why a passport goes through without the field and a DNI does not.

That is where the per-document split comes from, and it is how you will meet it at the front desk:

Two warnings about that table. First, NIF is not a document anyone will hand you: it is the code the DNI is declared under, because a Spanish person’s DNI number is also their NIF. Second, the four codes in the middle column are not written out in the specification, which points instead to a catalogue operation of the service itself; they are the values that catalogue returns, so they come from practice rather than from a document you can open yourself.

The second surname carries a discrepancy inside the specification itself that is worth knowing: the field table makes it mandatory only for NIF, while the version history describes it, from 3.0.0 on, as mandatory for NIF and NIE⁷. We ask for it in both cases, which is the only thing that satisfies either reading.

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 document is declared as NIF or NIE, because that will bounce.

At RegistroViajero we ask for the support number in exactly those two cases, and we warn the guest while they are filling the form rather than waiting for the eleven-at-night rejection. 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? The support number changes every time you renew your DNI, without exception. 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? IDESP is the same thing as the support number: it 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? The support number is not on the back of the DNI, 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? Looking up your support number without the card means reading it off the document anyway, since that is where it is printed: in practice you need it to hand or a photograph you took of the front.

What if a guest has no support number? A guest with no support number, because they travel on a passport or a foreign identity card, is reported without that field. It is only mandatory when the document is declared under the types NIF or NIE, meaning the DNI, the TIE and the EU citizen registration certificate.

Does the CAN work as a support number? The CAN does not work as a support number. It is six digits with no letters and exists so an NFC reader can access the document’s chip.