Merge fields in WHMCS are placeholders that dynamically insert specific information into email templates, making them more personalized and relevant to each recipient. These fields are replaced with actual data when the email is sent. Here are some common merge fields used in WHMCS:

1. Client Merge Fields:

   • {$client_id}: Client's unique ID.
   • {$client_name}: Client's full name.
   • {$client_first_name}: Client's first name.
   • {$client_last_name}: Client's last name.
   • {$client_email}: Client's email address.
   • {$client_address}: Client's address.
   • {$client_city}: Client's city.
   • {$client_state}: Client's state or province.
   • {$client_country}: Client's country.
   • {$client_postcode}: Client's postal or ZIP code.
   • {$client_phone}: Client's phone number.
   • {$client_company}: Client's company name.
   • {$client_group}: Client's group (e.g., "Default" or custom groups).
   • {$client_customX}: Custom client fields (replace X with the field ID).

2. Product/Service Merge Fields:

   • {$service_id}: Service's unique ID.
   • {$service_product}: Name of the product/service.
   • {$service_domain}: Associated domain name.
   • {$service_domain_id}: ID of the associated domain.
   • {$service_regdate}: Registration date of the service.
   • {$service_nextduedate}: Next due date for payment.
   • {$service_nextinvoicedate}: Next invoice date.
   • {$service_billingcycle}: Billing cycle (e.g., "Monthly").

3. Invoice Merge Fields:

   • {$invoice_id}: Invoice's unique ID.
   • {$invoice_num}: Invoice number.
   • {$invoice_date_created}: Date the invoice was created.
   • {$invoice_date_due}: Due date of the invoice.
   • {$invoice_total}: Total amount of the invoice.
   • {$invoice_subtotal}: Subtotal (excluding taxes and fees).
   • {$invoice_tax}: Tax amount.
   • {$invoice_balance}: Remaining balance due.

4. Ticket Merge Fields:

   • {$ticket_id}: Ticket's unique ID.
   • {$ticket_subject}: Subject of the ticket.
   • {$ticket_department}: Department handling the ticket.
   • {$ticket_priority}: Ticket priority level.
   • {$ticket_status}: Current status of the ticket.

These are just some of the commonly used merge fields in WHMCS. You can use these fields to customize email templates, invoices, support tickets, and other communications, making them more personalized and relevant to each recipient.