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Overview

Vatstack integration enables real-time VAT number validation during checkout, supporting the reverse charge mechanism for B2B transactions. When a customer provides a valid VAT number, the system verifies it against the Vatstack API and records the validated number and associated country on their customer record. This is relevant for businesses that:
  • Sell to other businesses across VAT jurisdictions
  • Need to apply reverse charge procedures for eligible B2B orders
  • Want automated validation of VAT numbers rather than manual verification

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How It Works

During checkout, customers can optionally enter their company’s VAT number. The system validates it in real time through the Vatstack API:
  1. Customer enters a VAT number (e.g. IE6388047V)
  2. The system sends the number to Vatstack for validation
  3. Vatstack checks the format, queries the relevant tax authority, and returns the result including the country code
  4. If valid, the VAT number and country are stored on the customer’s record
  5. The validated VAT number can then be used to determine whether reverse charge applies to the order

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Validation Outcomes

OutcomeWhat the customer sees
ValidVAT number and country are saved. The customer proceeds with the order.
Invalid format”VAT number lookup failed. Please confirm the details given are correct and try again.”
Service unavailable”An error was encountered whilst attempting to validate your VAT number. Please try again.”
The customer can retry after a failed validation or continue without a VAT number.

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Configuration

Vatstack is configured at the reseller level — all companies under a reseller share the same Vatstack credentials. To set up the integration:
  1. Navigate to the reseller settings
  2. Enter the Vatstack Secret Key
  3. Save
Once a valid secret key is configured, the VAT number input appears automatically during checkout for customers of companies under that reseller.
The secret key is stored encrypted in the database. If no key is configured, the VAT number field is not shown during checkout and customers see: “VAT number lookup is currently unavailable, so reverse charge procedure will not apply.”

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Customer Checkout Experience

When Vatstack is configured, the checkout includes a tax settings step with two parts:

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Entering a VAT Number

Customers see a VAT number field with help text: “Please provide your company’s VAT ID if the reverse charge mechanism should apply to your order.” The VAT number is validated immediately when submitted. If validation succeeds, the customer’s country is determined from the VAT number and stored alongside it.

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Providing Address Details

After the VAT number step, customers enter address details:
  • Address line 1 and 2
  • City
  • Region
  • Postcode

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What’s Stored on the Customer Record

After successful validation, the following is saved to the customer’s profile:
FieldDescription
VAT numberThe validated VAT number
CountryCountry determined from the VAT number
Verification statusWhether the VAT number was verified via Vatstack
Address detailsAddress, city, and postcode provided by the customer
These details persist across future orders — returning customers don’t need to re-enter their VAT information.
Some items may require the VAT number to be verified for reverse charges to apply. If the Vatstack service is temporarily unavailable during checkout, customers see: “Some items may require your VAT number to be verified in order for reverse charges to apply.”

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Restrictions

  • Vatstack configuration is per-reseller, not per-company — all companies under a reseller share the same credentials
  • VAT number validation requires a live connection to the Vatstack API — if the service is unavailable, validation cannot complete but the order can still proceed without a validated VAT number
  • The VAT number field only appears during checkout when valid Vatstack credentials are configured for the reseller