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Validate your customer's tax IDs

Validating your customer's tax IDs is a crucial step in tax compliance for B2B sales.

It is your business's responsibility to validate your customer's tax IDs, such as VAT or GST numbers, to apply reverse charge when needed. This means that you will not charge tax on the transaction, but rather your customer that is buying your products or services will be responsible for paying the tax.

To ensure that your customers' tax IDs are valid, use Quaderno's Tax IDs API. The process for validation is simple: submit a GET request with the country and tax ID you wish to validate:

curl --request GET \
--url ''

You can obtain one of the following values in response:

  • true if the tax ID is valid and represents an actual business.
  • false if the tax ID is not valid.
  • null if the external validation service is temporarily unavailable.

Note that some of the official validator services have daily maintenance windows. As a safeguard measure, we recommend not applying reserve charge when receiving a null response.

Check Quaderno's status page at for tax id validation related incidents, like unscheduled external validation service downtimes or exceptional scheduled maintenances.

At the moment, Quaderno can verify these Tax IDs:

Check our blog’s articles about how the reverse-charge mechanism works and how to check if a company is VAT registered to learn more.