In WHMCS, a "Multi-line Text Area" is a type of custom field that allows users to input multiple lines of text, as opposed to a single-line text input field. This type of field is useful for collecting more detailed or lengthy information from users.

For example, you might use a multi-line text area for fields like "Additional Comments," "Description," or any other scenario where users need to provide a paragraph or more of information.

Here's how you can create a multi-line text area custom field in WHMCS:

1. Log into WHMCS:

   Access your WHMCS admin panel using your administrator credentials.

2. Navigate to Custom Fields:

   • Go to "Setup" in the top menu.
   • Click on "Custom Client Fields" for client-related fields or "Custom Fields" for product-related fields, depending on where you want to add the field.

3. Create a New Custom Field:

   • Click the "Create New Field" button.

4. Select Field Type:

   • Choose "Multiline Text Box" as the field type.

5. Fill in Field Details:

   • Enter a name for the field (e.g., "Additional Comments").
   • Set any validation rules or options if needed.

6. Specify Field Location:

   • Select where the field should appear (e.g., client registration, client profile, etc.).

7. Choose Client Groups (if applicable):

   • Optionally, you can restrict the visibility of this field to specific client groups.

8. Save Changes:

   • Click the "Save Changes" button to create the new custom field.

Once created, this multi-line text area custom field will be available for clients to use when providing additional information in the specified areas of WHMCS.

Remember to consider the context in which you're using this custom field and whether it's most appropriate for clients to have a single-line or multi-line input for the information you're collecting.