Autofill a company form from a VAT number

The company block

Every B2B sign-up, checkout and supplier form asks for the same six fields: company name, legal form, street, postal code, city, VAT number. They are filled in by someone who wants to be finished with them, often on a phone.

That block is where B2B forms lose people, and where the quality of the invoice, the CRM record and the accounting export is decided.

What it changes

One field instead of six takes the step from about a minute to a few seconds. On a long sign-up, that is the cheapest reduction in abandonment available.

The slower effect matters more. When the name and address come from the register rather than a keyboard, the invoice reaches the right legal entity and the CRM stops holding the same company four times because somebody wrote SARL three different ways.

The lookup also says something about the number itself. One that resolves to nothing is worth flagging before the first zero-rated invoice rather than after.

Where the difficulty is

There is no single method, only one per country. Some publish their whole company repertory as open files of several gigabytes, names in one and addresses in another. Some expose an API of their own, with its own request shape and its own way of saying "not found". And in a few, no register will hand you the company behind a VAT number at all. Getting a company's name and address works through that country by country.

Multiply it by the countries you sell to, then add what is the same everywhere:

• The VAT number is rarely the company number. Sometimes the same identifier, sometimes derived from it, sometimes unrelated. There is no single join rule to write.
• The name is not always disclosed. A handful of member states publish validity and nothing else, so the form has to work when the name comes back empty.
• The address arrives as free text, in a different convention per country. Turning that into line1 / postalCode / city is a job of its own.
• The input is dirty. Spaces, dots, dashes, the country prefix typed or omitted, lowercase.
• A valid checksum proves nothing. The check digit of a struck-off company is still correct. Offline validation says the number is well formed, and stops there.
• Official sources go down. Not often, not never, not predictably. A form that waits for an answer before letting anyone submit breaks during somebody else's maintenance window.

One call, every country

One endpoint, one envelope, the same field names, whichever country the number belongs to. Vatlas answers the same way for every country it covers, and the country pages are the current list.

curl "https://api.vatlas.dev/v1/lookup/FR68005420120" \
  -H "Authorization: Bearer $VATLAS_KEY"

Response:

200 OK

{
  "data": {
    "vatNumber": "FR68005420120",
    "countryCode": "FR",
    "nationalNumber": "68005420120",
    "nationalId": "005420120",
    "name": "SOCIETE DES SUCRERIES DU MARQUENTERRE",
    "legalForm": "Autre SA à conseil d'administration",
    "status": "active",
    "address": {
      "line1": "32 CHEMIN DES GARENNES",
      "line2": null,
      "postalCode": "80120",
      "city": "SAINT-QUENTIN-EN-TOURMONT",
      "country": "FR"
    }
  },
  "meta": {
    "source": "SIRENE",
    "sourceDate": "2026-09-01",
    "sourceSince": "2026-06-01",
    "sourceUpdatedAt": "2026-02-13T11:07:03.000Z"
  }
}

Everything the form needs is already separated: one response field per form field, nothing to parse. The meta block names the register that answered and the date, which is what you keep if the record ever has to be justified.

Designing the form

• Normalise on the way in. Uppercase, strip spaces and punctuation, accept the number with or without its country prefix. Once, so the rest of the code sees one shape.
• Call from your own server. The API key identifies your account and belongs behind a route of your own, not in a front-end bundle. That route is also where you debounce a field firing on every blur.
• Fill the fields and leave them editable. Registers lag reality, and the person at the keyboard knows their own company better than a file published last month.
• Let the form submit either way. Short timeout, treat the lookup as an assist. An empty name is not an error; in a few countries it is the complete answer.
• Separate three outcomes on screen. Filled from the register, no company found, and no answer right now. The second is a soft warning beside the field. The third is your problem, not the customer's.
• Store what the register said, and when. If the exemption is questioned later, the answer is a dated record.

After the form

A company record is true on the day it is captured and stops being true afterwards. Vatlas can follow the companies you have onboarded and call back when a register changes its mind, so the correction lands before an invoice goes to the wrong place: see the monitor endpoint. For what each register has said over time, there is every source's answer.

Keep reading

• Getting a company's name and address
• Enriching a CRM from VAT numbers
• VAT numbers, country by country
• API documentation
• Pricing

Last updated 21 September 2026.