In some jurisdictions, you may need to fix the client's name, address, and tax ID to the values that existed when WHMCS generated the invoice. In these cases, subsequent changes to the client's profile data must not affect existing invoices.
Store Clients Data Snapshot
To fix client data to its state at invoice generation:
- Go to Configuration > System Settings > General Settings. or, prior to WHMCS 8.0, Setup > General Settings.
- Choose the Invoices tab.
- Check Store Client Data Snapshot.
- Click Save Changes.
After you do this, invoices will always use the client data that was present at invoice generation and will not change if you change the client's data. Invoices that the system generated before you enabled this setting will still change if the client's profile data changes.