instellix validates your customers' VAT IDs against official registers, so that your documents and tax decisions are based on verified data.

Activate VAT ID validation

VAT ID validation is activated per billing group. Navigate to: Billing > Billing Groups, open the details of the billing group and click "Edit". Enable the "VAT ID check" toggle and save.

Only billing groups with VAT ID validation enabled trigger a validation. For when checks run, the possible results (VALID / INVALID / FAILED) and their impact on tax calculation, see the section "The VAT-ID check during the billing run" below.

Where you see the result

The validation result is shown on the document details page in the webportal ("VAT ID validation result"). In addition, each check triggers a vatId.checked notification.

Via API

VAT ID validation is configured per billing group via the Tax Service Billing Group Configuration endpoints.

The VAT-ID check during the billing run

The VAT-ID Check feature allows Instellix to validate European VAT Identification Numbers automatically during invoice creation.

The validation is performed in real time via the official VIES (VAT Information Exchange System) interface provided by the European Commission: https://ec.europa.eu/taxation_customs/vies

The validation result directly influences tax calculation and is stored together with the invoice document for audit purposes.

If you are interested in activating this feature, activate it yourself per billing group as described above.

Configuration

The VAT-ID Check must be configured on Billing Group level.

Only billing groups with VAT-ID validation enabled will trigger a validation during invoice creation.

When is a VAT-ID check performed?

A VAT-ID validation is executed during invoice creation only if all of the following conditions are met:

1. Tax calculation is enabled for the invoice (not custom provided)
2. VAT-ID validation is activated in the assigned Billing Group.
3. A VAT-ID is present in the invoice address.
4. The VAT-ID contains a valid EU prefix.

If one of these conditions is not fulfilled, no validation request to VIES is sent.

This selective validation ensures stable bill run performance.

Result caching

Validation results are cached for 24 hours per VAT-ID. If the same VAT-ID needs to be validated again within that period, the stored result is reused instead of sending a new validation request — this keeps billing runs fast and stable.

Note that this also delays status changes: if a VAT-ID was validated with a negative result and the registration is corrected afterwards, the new status may only take effect once the cached result has expired — that is, after up to 24 hours.

Validation Results

The VAT-ID check can return one of the following results:
• VALID
• INVALID
• FAILED (e.g., technical error or VIES service unavailable)

Impact on Tax Calculation

If Instellix determines the taxes for an invoice, the VAT-ID validation result directly influences which tax rule is applied.

The system distinguishes between tax rules:
• with VAT-ID
• without VAT-ID

The following logic applies:

Important Notes
• This logic applies only if tax calculation is handled by Instellix.
• If taxes are externally provided (e.g., client-calculated taxes), no tax rule adjustment is performed.
• A result of FAILED is intentionally treated like INVALID to ensure compliance in case of technical issues or temporary unavailability of the VIES service.
• The applied tax rule always follows the configured country-specific tax setup.

Which document types are validated

The VAT-ID check is not limited to invoices: it also applies to credit notes, deposit invoices, and self-billing invoices. Credit notes are handled in a special way — they do not trigger a new validation but take over the validation result of the original invoice they refer to, so a credit note is always based on the same validation result as its original document.

Storage

The validation result is:
• Stored as an attachment on the generated document
• Can optionally displayed directly on the document
• Displayed in the Web Portal on document level

This guarantees traceability and auditability of VAT decisions.

Notification

Instellix provides a dedicated notification: VAT-ID-Validation-Result

This notification can be used to programmatically retrieve the validation result.

More information: https://docs.instellix.io/reference/further-notifications#vat-id-validated