The Invoices tab allows you to configure how WHMCS generates and sends invoices and applies late fees.

You can access this tab at Configuration () > System Settings > General Settings.

Continuous Invoice Generation #

Whether to use Continuous Invoice Generation. When you enable Continuous Invoice Generation, the system creates invoices regardless of whether unpaid invoices exist for the service. Use this setting when the product has a minimum term and the client must pay all invoices.

• The system generates invoices if the service status is Pending, Active, or Suspended.
• The system will not generate invoices if the service status is Completed, Cancelled, or Terminated.

If you disable this, the system will not generate additional invoices until the client pays the unpaid invoice.

Enable Metric Usage Invoicing #

Whether to bill any enabled billing metrics for a given product at the time of service renewal. Each metric generates a line item that reports the total usage value and a breakdown of the system’s calculation of the billed amount.

• The line item’s description will vary based on the pricing scheme type, the pricing brackets, and the incurred usage.
• All possible descriptions are available for translation via the language file system.

Service termination triggers the creation of a one-time usage invoice for current snapshot metrics and unbilled usage to date. This will look similar to the standard renewal invoice excluding the service.

Enable PDF Invoices #

Whether to attach a copy of the invoice to invoice notification emails as a PDF file.

PDF Paper Size #

The size of the individual pages in a PDF invoice. For example, the A4 paper size is slightly larger than a standard letter, allowing you to include more information per page.

PDF Font Family #

The font to use in PDF invoices and quotes.

Store Client Data Snapshot #

Whether to save clients’ name, addresses, and custom field data (for example, VAT numbers) during invoice generation. Both Client Area and PDF invoice views will display the name and address information as it was at the time of initial creation. Editing the client or billing contact only causes future invoices to change; existing invoices will keep their current addressees.

After you enable this, the system will begin to save invoice data in this way.

Enable Mass Payment #

Whether to allow clients to pay several invoices in one transaction using the options in the Due Invoices section of the Client Area Homepage.

Clients Choose Gateway #

Whether to allow changes to the payment gateway that customers use to pay each invoice. If you disable this, each invoice must use the payment gateway that the client chose during signup.

Group Similar Line Items #

Whether to group similar items on a single invoice. If you enable this setting, WHMCS automatically groups products, services, addons and domains into a single invoice if they are due on the same date with the same payment method and the same person. The customer only receives a single invoice and only needs to make a single payment. This, then, reduces your transaction fees.

For example, enabling this automatically groups any identical line items on these invoices into a quantity x description format. For example, three entries of Monthly Lease $15.95 would become one line item for 3 x Monthly Lease @15.95 $47.85.

Cancellation Request Handling #

Whether to cancel any unpaid invoices for a service automatically when a client submits a cancellation request.

Automatic Subscription Management #

Whether to automatically cancel PayPal® Basic and 2CheckOut subscriptions if any of the following circumstances occur:

• The client or an admin submits a cancellation request.
• An admin cancels the order or sets it to fraud via the Admin Area.
• The API passes cancelsub=true to cancel the order or set it to fraud.
• The client or an admin submits an upgrade order for the service.

Enable Proforma Invoicing #

Whether to cause invoices to display Proforma invoice when the status is Unpaid, Refunded, Cancelled, Collections, or Payment Pending. Invoices will display Invoice when the status is Paid.

Sequential Paid Invoice Numbering #

Whether to number paid invoices separately from unpaid invoices.

Sequential Invoice Number Format #

The format for sequential invoice numbering. The default value of this is {NUMBER}, which will contain only the value from Next Invoice Number. The format can contain any text in the invoice number that the client will see.

Next Paid Invoice Number #

A number to use to number the next invoice that WHMCS generates.

Late Fee Type #

Whether the one-time fee on late payments is a percentage or a fixed amount.

Late Fee Amount #

An amount to charge to customers who fail to pay an invoice by the due date.

Set this to 0 to disable late fees.

Late Fee Minimum #

The minimum amount to charge for late fees. For example, if the late fee is $0.50 and this value is 1.00, the system will charge the client $1.00.

Accepted Credit Card Types #

The types of credit cards to accept via your payment gateway.

Issue Number/Start Date #

Whether to prompt customers to enter the issue number and start date that some card types require.

Invoice # Incrementation #

The amount by which each invoice number will increase. For example:

• Entering 1 would cause the first four invoice numbers to be 1, 2, 3, and 4.
• Entering 2 would cause the first four invoice numbers to be 1, 3, 5, and 7.

Credit Note Number Incrementation #

The amount by which each credit note number will increase. For example:

• Entering 1 would cause the first four credit note numbers to be 1, 2, 3, and 4.
• Entering 2 would cause the first four credit note numbers to be 1, 3, 5, and 7.

Debit Note Number Incrementation #

The amount by which each debit note number will increase. For example:

• Entering 1 would cause the first four debit note numbers to be 1, 2, 3, and 4.
• Entering 2 would cause the first four debit note numbers to be 1, 3, 5, and 7.

Invoice Starting # #

The invoice number that WHMCS will start with when it generates the next invoice. This is useful if you want to start invoicing at a number other than 1 or start invoices for a new year from a new number.

• Only enter numbers that are greater than the most recent invoice’s number.
• Do not enter a number unless you specifically want to change the invoice numbering.

Invoice Immutability #

The compliance state to enforce for invoices. This setting controls whether you can edit invoices after they leave the Draft status and whether the system generates credit and debit notes.

You can select the following options:

Last modified: 2026 September 30