Duplicate Transactions

Troubleshoot and resolve issues with multiple duplicate transactions occurring for the same service or invoice.

E-Invoicing

The E-Invoicing addon module sends your invoices to a third-party service. That service creates a Peppol BIS Billing 3.0 e-invoice and exchanges it with the tax authority, which helps you meet EU e-invoicing mandates. It is in a limited release for installations in Belgium.

E-Invoicing Configuration Errors

Troubleshoot and resolve validation errors when you save settings for the E-Invoicing addon module, including invalid value formats and missing license credentials.

Enable Proforma Invoicing

Enable proforma invoicing, which ensures sequential invoice numbers for paid invoices. Some countries' accounting practices require this.


Invoices

The Invoices tab in General Settings allows you to configure how WHMCS generates and sends invoices, enforces invoice immutability, and applies late fees.


Merge Invoices

Merge invoices to combine multiple separate invoices into a single comprehensive invoice and delete the previous separate invoices.




Regenerate Invoices

Regenerate an invoice for a specific period, or regenerate old invoices after moving to WHMCS to ensure accurate historical records.

Reissue an Invoice

Reissue an invoice to correct immutable values like the invoice date, invoice number, due date, or tax rate after an invoice leaves Draft status.

Skip an Invoice

Skip a specific invoice without charging the customer for that billing period. The system will resume billing on the next due date.

Snapshot Customer Invoice Data

Configure WHMCS to automatically store client data (the client's name, address, and tax ID) at the time of invoice generation.



E-Invoicing Invoice Export Errors

Troubleshoot and resolve invoices that fail to export or show an Error status in the E-Invoicing addon module, including eligibility checks and retry limits.

Invoice Already Submitted Errors

Troubleshoot and resolve changes to an invoice that you already exported to the e-invoicing service, which the system treats as immutable.

E-Invoicing Status Update Errors

Troubleshoot and resolve invoices with an e-invoicing status that does not update after export, including webhook delivery and 401 errors.