E-Invoicing Configuration Errors
Problem
When you save the E-Invoicing addon module settings at Configuration () > System Settings > Addon Modules, the system displays a validation error and does not save your changes. The error message lists the specific information that failed. For example:
The tax ID is invalid.
The postcode is invalid.
You must provide both license credentials or they must be empty.
Cause
This error occurs when one or more configuration values do not meet the addon module’s validation rules, or when you only provide one of the two license credentials.
The configuration settings use the following rules:
| Setting | Required? | Rule |
|---|---|---|
| License ID | ✓ | This value accepts letters (a–z), digits (0–9), dashes (-), and asterisks (*) only. It allows a maximum of 50 characters. |
| License Key | ✓ | This value accepts letters (a–z), digits (0–9), dashes (-), and asterisks (*) only. It allows a maximum of 50 characters. |
| Company Name | ✓ | This value allows a maximum of 50 characters. |
| Tax ID | Conditional | This value is required when you select the Tax Support checkbox at Configuration () > System Settings > Tax Configuration. It accepts letters (a–z), digits (0–9), spaces, and the ., /, and - characters only, and allows between 5 and 20 characters. |
| ✓ | This value must be a valid email address. | |
| Address | ✓ | This value allows a maximum of 100 characters. |
| City | ✓ | This value allows a maximum of 50 characters. |
| Postcode | ✓ | This value accepts digits (0–9), letters (a–z), dashes (-), spaces, and the / character only. It allows between 4 and 20 characters. |
| Country | ✓ | You must select a country from the menu. During the limited release, select Belgium. The addon module supports installations in Belgium only, and selecting other countries may return errors. |
| Phone | Optional | This value accepts between 7 and 15 digits with no spaces or special characters. |
| Audit Log Retention (Days) | Optional | This value sets how many days the system retains audit data in the mod_einvoicing_audit_log table on your WHMCS instance. It defaults to 180 days. |
Solution
To resolve this error:
- Read the error message that the system displays. It names the specific information that failed validation.
- Correct the information so that it meets the rules in the table above.
- If the error includes a You must provide both license credentials or they must be empty message, make certain that you enter both the License ID and the License Key values, or leave both empty.
- Click Save Changes again.
If validation errors continue after you correct all of the information, or if the message does not identify a specific value, contact WHMCS Technical Support.
Last modified: 2026 September 17