Open the client's Products/Services tab and note the service's billing cycle, recurring amount, Next Due Date, promotion and payment method. Review related invoices, including unpaid renewals and pending upgrade orders. If continuous invoicing is enabled, examine the next invoice schedule as well.

1. Confirm the new billing period, effective date and amount with the billing owner and customer agreement.
2. If changing the cycle, select the intended cycle and decide whether to calculate the price from current product settings or preserve an explicitly agreed custom price.
3. Use Auto Recalculate on Save only when recalculation is intended. Review the resulting Recurring Amount before saving.
4. Set the service's Next Due Date to the agreed next payment date, taking the already paid period into account.
5. Review existing invoices separately. A service change does not automatically rewrite a published invoice or an external fixed-amount subscription.
6. Save, reopen the service and verify the final values against the change record.

If the change creates an extra partial period, calculate and document the charge using the approved billing method. Do not treat an arbitrary date extension as payment. Review any PayPal or other provider subscription whose schedule or amount may now differ.

Changing a date can make a service immediately eligible or ineligible for automated suspension. Review the next automation run and any manual exception before applying a past date.

Check the first invoice generated after the change for the correct period, amount and gateway. If an old invoice remains payable, resolve it through the appropriate adjustment or reissue process. Keep the original and new dates in the internal note so future staff can explain the transition.

• Set up prorated WHMCS product billing
• Correct a WHMCS invoice without losing its audit trail
• Resolve duplicate recurring payment subscriptions
• Apply a hosting package change from a WHMCS service

• WHMCS Products/Services tab
• WHMCS billing logic
• WHMCS: reissue an invoice
• WHMCS PayPal Basic module