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WHMCS – Invoicing Setup

Setting the Starting Number

WHMCS allows you to set the next invoice number that is generated. This is useful for if you want to start invoicing at a number other than 1 or start invoices for a new year from a new number. You do this as follows:

  • Go to Setup > General Settings > Invoices tab
  • Enter the next number to assign in the “Invoice Starting #” field
  • Click Save

The value will then disappear from the field but the next invoice will be assigned that number.

Automatic Invoice Generation

WHMCS automatically generates invoices for recurring products and services in advance of the due date.

You can configure exactly how far in advance invoices are generated in Setup > Automation Settings > Billing Settings. By default it is 14 days.

Using the “Advanced Settings’, it is also possible to configure the number of days in advance to generate invoices on a per billing cycle basis.

The cron performs the generation each day so it is important you have the Cron Tasks configured.

Invoice Reminders & Notices

WHMCS allows you to send:

  • A maxmimum of 1 reminder prior to the invoice reaching the due date
  • Up to 3 overdue reminders once the invoice has passed the due date

You can configure when you would like these notices go out in Setup > Automation Settings > Billing Settings.

Group Similar Line Items

By enabling this option in Setup > General Settings > Invoices tab any identical line items will automatically be combined into one summarised quantity format. For example:

 Monthly Lease $15.95
 Monthly Lease $15.95
 Monthly Lease $15.95


 3 x Monthly Lease @ $15.95  $47.85

This format is only used in the client (printable) invoice, the admin area invoice will still display each item on an individual line.

Automatic Grouping of Items

WHMCS automatically groups products, services, addons and domains due on the same date, with the same payment method and by the same person onto a single invoice.

By doing this, it means the customer only receives a single invoice, only needs to make a single payment, and reduces transaction fees for you the merchant.

Should you have a client for which you do not wish this grouping to occur for, it can be disabled either by the Separate Invoices setting within a clients profile, or the same setting offered within client groups.

Continuous Invoice Generation

Continuous Invoice Generation refers to whether invoices are created for items that are unpaid. It is best explained through the use of an example.

Take for example a hosting account paid monthly. The user places their order in January. They receive an invoice and they pay their invoice. In the following month, the user gets their next invoice and they pay that. Then in March, the user receives their invoice but they don’t pay it because they no longer wish to use the account or simply because they miss the emails about it. With continuous invoice generation disabled, the user would not receive any further invoices until the March invoice has been paid. However, with continuous invoicing enabled, the user would receive invoices every month until the account is set to terminated, regardless of whether the item has been paid for or not.

With Continuous Invoice Generation enabled, any product that is Active, or Suspended will continue to invoice regardless of the status of its previous invoice(s). Pending, Completed, Cancelled or Terminated services will not generate invoices.

Enabling Continuous Invoicing

To enable this feature, go to Setup > General Settings > Invoicing and tick the checkbox next to this setting. After enabling this option, if there are then users who are due invoices for months which have not yet been invoiced, there will be one invoice generated on each cron run for the user for the following days after enabling this.

Proforma Invoicing/Sequential Invoice Numbering

This feature is primarily aimed at EU based companies where for accounting reasons, it is sometimes necessary to ensure paid invoice numbers are sequential. This feature in WHMCS can of course be used by all though.

Enabling Sequential Invoice Numbering

  1. To enable this feature, begin by going to Setup > General Settings
  2. Then click on the Invoices tab
  3. Next, tick the box labelled “Sequential Paid Invoice Numbering”
  4. In the field below, you can then specify the format you want to use for the numbering – it doesn’t just have to be a number – you could for example include your companies initials and the year to differentiate invoices for each year – eg. WHMCS2007-{NUMBER} – {NUMBER} placeholder gets replaced with that invoices number
  5. The final field allows you to set the next number to be assigned to an invoice. Each time an invoice is paid, the number increases by 1. You can alter the number here, such as when removing an invoice or at the beginning of a new year if you want to start at 1 again.

That’s all there is to it! Sequential invoice numbering is now enabled and each time an invoice is paid, the next number in the sequence will be applied.

Proforma Invoicing

The sequential numbering is most often used in conjunction with proforma invoicing. Invoices will display the term “Proforma invoice” whilst in unpaid status and “Invoice” once paid. This can be enabled under Setup > General Settings > Invoices tab > Enable Proforma Invoicing’

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