When a new invoice is created, the users have the option to select a custom invoice form. In some cases, the Payment subtab on the Billing tab is not displayed on the invoice.
In order to make the Payment subtab visible on the Billing tab, please follow the steps below:
1. Navigate to Customization > Forms > Transaction Forms.
2. Choose the custom invoice form which is used for new invoices and Edit.
3. On the Lists tab > Billing: Payment subtab, check the Gift Certificate check box in the Show column.
Note: In order to be able to display the Billing: Payment subtab on the Lists tab of an invoice record, enable the Gift Certificates feature in Setup > Company > Enable Features > Items & Inventory.