# What Is a VAT Number? Formats, Validation, and When You Need One

> What is a VAT number? Learn VAT number formats by country, how to check a VAT number in VIES or with HMRC, and when a SaaS business needs one.
- **Author**: Deepak Jangir
- **Published**: 2026-09-29
- **Category**: Tax, Compliance
- **URL**: https://dodopayments.com/blogs/en/what-is-a-vat-number

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A VAT number is the unique identifier a tax authority assigns to a business that is registered for value added tax. It proves the business is part of the VAT system, lets it charge and reclaim VAT, and tells its suppliers whether a cross-border sale can be invoiced without VAT under the reverse charge.

It is also called a VAT ID, VAT registration number, or VATIN. In the EU it starts with a two-letter country prefix, such as DE or FR, followed by a national block of digits or characters.

For a SaaS company, the VAT number decides whether a B2B invoice carries VAT, whether it survives an audit, and whether you owe tax you never collected. This guide covers formats, validation, and when you need one.

## What Is a VAT Number Used For?

A VAT number does three jobs.

- **It identifies the business to the tax authority.** Every VAT return, payment, and audit is tied to it.
- **It appears on invoices.** A VAT invoice issued by a registered business must show the seller's VAT number, and on cross-border B2B sales it must usually show the buyer's too.
- **It signals B2B status across borders.** When a business customer in another EU country gives you a valid VAT number, the supply of services is normally taxed where the customer is, and the customer accounts for the VAT through the reverse charge.

For software sellers the third job matters most: a valid VAT number is the evidence that lets you remove VAT from the invoice. Our [reverse charge VAT guide](https://dodopayments.com/blogs/reverse-charge-vat) walks through that mechanism in detail.

There is no single "EU VAT number" for ordinary businesses. Each member state issues its own, so a company registered in several countries holds one number per country.

## What a VAT Number Looks Like: Formats by Country

The structure is always the same idea: country prefix, then a national block. The length and character rules differ. The table below covers the formats you will see most often on SaaS checkouts. The example patterns use 9 for a digit and L for a letter, and they are placeholders, not real registrations.

| Country | Prefix | Format after prefix | Example pattern |
| --- | --- | --- | --- |
| Germany | DE | 9 digits | DE999999999 |
| France | FR | 2 characters (letters or digits) + 9 digits | FRXX999999999 |
| United Kingdom | GB | 9 digits (12 for some group branches) | GB999999999 |
| Netherlands | NL | 9 digits + the letter B + 2 digits | NL999999999B99 |
| Ireland | IE | 8 or 9 characters, mixing digits and letters | IE9999999L or IE9999999LL |
| Spain | ES | 9 characters, first and/or last may be a letter | ESL9999999L |
| Italy | IT | 11 digits | IT99999999999 |
| Austria | AT | the letter U + 8 digits | ATU99999999 |
| Belgium | BE | 10 digits, starting with 0 or 1 | BE0999999999 |
| Poland | PL | 10 digits | PL9999999999 |
| Greece | EL | 9 digits | EL999999999 |

A few details trip people up.

- **Greece uses EL, not GR.** The VAT prefix follows the Greek language code rather than the ISO country code. A form that only accepts ISO country codes will reject valid Greek numbers.
- **Austria's U is part of the number.** ATU12345678 is correct. AT12345678 is not.
- **The French block embeds the SIREN.** The last nine digits are the company's SIREN registration number.
- **The Dutch B is literal.** NL numbers always contain the letter B between the nine digits and the two-digit suffix.
- **UK numbers stopped being EU numbers after Brexit.** GB numbers are validated with HMRC, not in the EU system. Businesses in Northern Ireland trading goods with the EU use an XI prefix, which does appear in the EU system.

Treat these formats as a first filter only. A string can match the pattern perfectly and still belong to nobody.

## VAT Number vs Other Tax IDs (EIN, GSTIN, ABN)

A common checkout error is the wrong kind of number: a US company pastes its EIN into a VAT field, or an Indian company enters its PAN instead of its GSTIN.

| Identifier | Country | Issued by | What it is for | Typical format |
| --- | --- | --- | --- | --- |
| VAT number | EU member states, UK | National tax authority | Registration for VAT, invoicing, reverse charge | Country prefix + 8 to 12 characters |
| EIN | United States | IRS | Federal income tax, payroll, bank accounts | 9 digits, written XX-XXXXXXX |
| GSTIN | India | GST network | Registration for GST | 15 characters, starting with a 2-digit state code and containing the PAN |
| ABN | Australia | Australian Business Register | General business identifier, linked to GST registration | 11 digits |
| Business Number (GST/HST) | Canada | CRA | GST/HST account | 9 digits + RT + 4 digits |

The key point: an EIN is not a VAT number, and it is not a sales tax number either. The US has no VAT, and sales tax registration happens state by state with separate permit numbers. If you sell into both regions, our comparison of [VAT vs sales tax for SaaS](https://dodopayments.com/blogs/vat-vs-sales-tax-saas) explains why the two systems need different handling at checkout.

A single "Tax ID" field on your checkout will receive all of these, so validation must key off the customer's country.

## Do I Need a VAT Number?

Whether you need your own VAT number depends on where you are established, where your customers are, and whether they are businesses or consumers.

### If you are established in the country

Most countries set a domestic registration threshold based on turnover. The UK threshold is GBP 90,000 of taxable turnover. EU thresholds vary widely by member state, and some countries such as Spain have no domestic threshold at all. Below the threshold, registration is usually optional. Above it, it is mandatory. Our [VAT and GST registration thresholds guide](https://dodopayments.com/blogs/vat-gst-registration-thresholds) lists the figures for 30+ countries.

### If you sell digital services from outside the country

This is where most SaaS founders get caught. For B2C sales of digital services, many countries apply no threshold to non-established sellers. A US company selling a subscription to a consumer in France is generally liable for French VAT from the first sale, and in the UK a non-established business selling digital services to UK consumers must register regardless of turnover.

Within the EU, businesses established in a member state get a shared EUR 10,000 threshold for cross-border B2C digital sales before destination-country VAT applies. Sellers from outside the EU do not get that allowance.

### OSS and IOSS in brief

Instead of registering in 27 countries, you can use the EU One Stop Shop (OSS): register in one member state and file a single quarterly return covering B2C sales across the EU. Non-EU sellers of services use the non-Union OSS scheme. The Import One Stop Shop (IOSS) covers low-value imported goods of up to EUR 150, which matters for physical products rather than SaaS.

For a full walkthrough of the EU rules, see the [EU VAT guide for SaaS in 2026](https://dodopayments.com/blogs/eu-vat-saas-guide-2026).

### When B2B changes the answer

If your customers are VAT-registered businesses in other countries, the reverse charge usually moves the VAT obligation to them, so you may not need to register there. That only works if you can prove they are businesses, which is what a validated VAT number does.

## How to Check a VAT Number

A format check says a number could exist. A registry check says it exists and is active now. B2B zero-rating needs the second.

### EU numbers: VIES

The European Commission's VIES (VAT Information Exchange System) is a search tool that queries each member state's national VAT database in real time. You enter the country and the number, and VIES returns whether the number is valid for intra-EU transactions. Depending on the member state, it may also return the registered name and address.

Things to know about VIES:

- **It is a lookup, not a database.** If a national system is down, VIES cannot answer.
- **Validity is point-in-time.** A number valid today can be deregistered next month. Check at the point of sale, not once at onboarding.
- **You can get a consultation number.** If you enter your own VAT number as the requester, VIES returns a consultation reference you can keep as proof that you checked.

### UK numbers: HMRC

GB numbers are checked with HMRC's online VAT number checker. It confirms whether the number is valid and returns the registered business name and address. As with VIES, you can obtain a reference for your records when you supply your own UK VAT number.

Outside the EU and UK, Australia's ABN Lookup confirms ABNs and GST status. Many other countries have no public real-time registry, so format and checksum validation is the realistic limit.

### Why validation comes before zero-rating

Here is the sequence you should follow on every B2B sale.

```mermaid
flowchart LR
    A["Customer enters VAT number"] --> B{"Format and checksum OK?"}
    B -- No --> C["Reject or charge VAT"]
    B -- Yes --> D{"Registry lookup: VIES / HMRC"}
    D -- "Invalid" --> C
    D -- "Valid" --> E["Store evidence and apply reverse charge"]
    E --> F["Issue invoice showing both VAT numbers"]
```

If you zero-rate a sale and the VAT number turns out to be invalid, the supply was taxable. The tax authority can assess the uncharged VAT against you, with interest.

**Worked example (illustrative figures).** A UK SaaS seller invoices a Dutch company EUR 5,000 for an annual plan and applies the reverse charge. The customer's VAT number was deregistered two months earlier. The sale should have carried Dutch VAT at the standard 21%, so the seller now owes EUR 1,050 out of its own margin, because the EUR 5,000 it received was the whole price.

## Why VAT Numbers Matter on SaaS Invoices

A VAT invoice for a cross-border B2B service is not complete without the right identifiers. At a minimum it should carry:

- The seller's VAT number
- The buyer's VAT number
- A clear statement that the reverse charge applies, instead of a VAT amount
- The standard invoice details: a unique [sequential invoice number](https://dodopayments.com/blogs/invoice-number), dates, the buyer's legal name and address, and the net amount

If a customer later tells you their VAT number was wrong, you cannot edit the original invoice. You issue a [credit memo](https://dodopayments.com/blogs/credit-memo) against it and re-invoice with the correct details. The same principle applies to the difference between the tax document and the payment confirmation, which our [invoice vs receipt](https://dodopayments.com/blogs/invoice-vs-receipt) explainer covers.

E-invoicing mandates are also making these fields machine-checked, so a malformed buyer VAT ID can mean a rejected invoice. See our overview of [global e-invoicing compliance for SaaS](https://dodopayments.com/blogs/e-invoicing-compliance-global-saas).

## Common VAT Number Mistakes

These are the errors that show up again and again in B2B billing systems.

- **Missing country prefix.** A German customer types 123456789 instead of DE123456789. Some systems silently accept it, which leaves you with a number nobody can verify later. Normalise input by adding or requiring the prefix based on the billing country.
- **Trusting format-only checks.** A regular expression proves the shape, not the registration. Zero-rating on a pattern match is the single biggest source of assessed VAT in this area.
- **Not storing validation evidence.** Auditors ask how you knew the customer was a business on the date of sale. Keep the lookup result, timestamp, and consultation reference.
- **Checking once and never again.** Numbers get deregistered, so validate on each new purchase.
- **Letting a validation outage zero-rate the sale.** If VIES times out, the safe default is to charge VAT, not to assume the number is fine.

UK sellers also face digital record-keeping rules, covered in our [Making Tax Digital guide for UK SaaS](https://dodopayments.com/blogs/making-tax-digital-uk-saas).

## How a Merchant of Record Handles VAT Numbers

If you sell through a [Merchant of Record](https://dodopayments.com/blogs/what-is-a-merchant-of-record), the MoR is the legal seller. It holds the VAT registrations, charges and remits the tax, and issues the invoices. That also means VAT number collection and validation become part of its checkout rather than a system you build.

With Dodo Payments, checkout lets a customer choose to purchase as a business and enter a business tax ID plus business name, as described in the [B2B payments documentation](https://docs.dodopayments.com/features/b2b-payments). For EU member states, Great Britain, and Australia, checkout runs format and checksum validation and a live registry lookup against VIES, HMRC, and ABR respectively, then autofills the registered legal name. For other countries it runs format and checksum validation.

When the tax ID is valid, the invoice shows the customer's tax ID, and where the law applies, tax is not charged and the invoice is clearly marked as reverse charge. An invoice is generated automatically for every successful payment and every subscription renewal, as covered in the [invoice generation docs](https://docs.dodopayments.com/features/invoice-generation).

### Collecting a VAT number at checkout

If you already know the buyer's VAT number, for example from a sales-led deal, you can pass it when you create the session. Setting `require_tax_id` makes the field mandatory for business buyers, which is useful for B2B-only plans.

```typescript
import DodoPayments from "dodopayments";

const client = new DodoPayments({
  bearerToken: process.env.DODO_PAYMENTS_API_KEY,
  environment: "test_mode",
});

const session = await client.checkoutSessions.create({
  product_cart: [{ product_id: "pdt_abc", quantity: 1 }],
  customer: { email: "buyer@acme.com" },
  tax_id: "GB123456789",
  customer_business_name: "Acme Corp Ltd",
  feature_flags: {
    allow_tax_id: true,
    require_tax_id: true,
    allow_customer_editing_business_name: true,
  },
  return_url: `${process.env.APP_URL}/return`,
});
```

The business name only appears on the invoice when the purchase is B2B, a tax ID is present, and `customer_business_name` is non-empty, so pass both fields together. The full set of session options is in the [checkout session reference](https://docs.dodopayments.com/developer-resources/checkout-session), and the [checkout features page](https://docs.dodopayments.com/features/checkout) covers the customer-facing flow. If your finance team needs the PDF programmatically, the [Get Invoice endpoint](https://docs.dodopayments.com/api-reference/payments/get-invoice) returns it for any payment.

For purchase orders and other invoice-based flows, see our guide to [B2B payments](https://dodopayments.com/blogs/b2b-payments).

## FAQ

### Is a VAT number the same as a company registration number?

No. A company registration number comes from the business registry and identifies the legal entity, while a VAT number comes from the tax authority and shows the business is registered for VAT. In some countries they share digits, such as the French SIREN appearing inside the VAT number, but they are separate identifiers.

### Can a US company have an EU VAT number?

Yes. A US company that registers for VAT in a member state, or for non-Union OSS, receives an identifier from that country. Many avoid this by selling through a Merchant of Record.

### What happens if VIES says a VAT number is invalid?

Charge VAT at the customer's local rate and ask them to confirm the number. Common causes are a missing prefix, a typo, or a number not activated for intra-EU transactions.

### Do I need to show my own VAT number on invoices?

If you are VAT registered, yes. A VAT invoice must show the seller's VAT number, and for cross-border B2B services it should also show the customer's number and a reverse charge statement.

### Does a sole trader have a VAT number?

Only if they are registered for VAT. A sole trader below the domestic threshold is often not registered, which means they are treated like a consumer for cross-border VAT purposes and you should charge VAT on the sale.

## Conclusion

A VAT number is a tax authority's proof that a business is registered for VAT, and for anyone selling software across borders it decides whether an invoice carries VAT or the reverse charge. Knowing the format of each country's VAT number helps you catch typos. Checking the number in VIES or with HMRC, and keeping the evidence, is what actually protects you.

If you would rather not build validation, registrations, and compliant invoicing yourself, [Dodo Payments](https://dodopayments.com) handles them as your Merchant of Record, with live tax ID lookups at checkout and automatic invoices on every payment. See the [pricing page](https://dodopayments.com/pricing) for what is included.
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