Specific billing logic governs the automation for many of your business's most important tasks, including ordering, payments, and provisioning. Issues with invoices and invoice generation can be due to many causes, some of which may not be obvious at first. After invoice generation, you can easily manage your clients' invoices, including payment, splitting invoices, cancelling them, and more. The system uses your Automation Settings configuration to determine when to generate invoices for your customers and how to format them. Invoice and quote PDF files use a customizable template file system in the templates directory of the active WHMCS system theme. The Invoices tab in the Client Profile allows you to view and manage all of the client's invoices. Troubleshoot and resolve issues with domain renewal invoices that the system has set to Cancelled. Update the payment gateway configuration to change the invoice payment instructions for Mail in Payment or Bank Transfer invoices. Change the Pay To Text address on generated invoices. Newly-generated invoices will use the new address after you save this change. Configure WHMCS to send payment reminders before customers' payment dates and to send additional notices after a bill is overdue. Convert invoices from one enabled currency to another before the client makes payment using the Convert To For Processing option. Mass Payment allows customers to quickly and easily pay for multiple invoices in a single transaction, reducing your processing costs. Manually generate an invoice for a client's service, product or domain addon, or domain renewals before the system generates the next automated invoice. Automatically generate separate invoices for services that have the same due date, either for individual clients or client groups. Customize the invoice number that the system generates for each invoice by configuring the Custom Invoice Numbering Format setting. Troubleshoot and resolve issues with duplicated invoices for different dates. Troubleshoot and resolve issues with the system generating duplicated invoices for the same date. Troubleshoot and resolve 1062 Duplicate entry for key tblinvoices.PRIMARY errors. Troubleshoot and resolve issues with multiple duplicate transactions occurring for the same service or invoice. Enable proforma invoicing, which ensures sequential invoice numbers for paid invoices. Some countries' accounting practices require this.