Custom fields are extra fields that you can enable based on your business needs.

Example: If you are in the tours and travels business and you want to print the journey date on your invoice, then you can enable date custom field in the sales invoice that will allow you to add a journey date while creating an invoice and it will print that date on the invoice.

To create a custom field follow the steps below

Step 1: Click on the profile icon and select Settings

Step 2: Select Custom Field

Step 3: Select Sale Invoice,
Enable Extra Date 1, and enter Journey Date in Extra Date 1 Label

Step 4: Now when you create a new invoice, it will show the option to enter the Journey Date

and when you print the invoice it will show the Journey Date on invoice

There are different types of custom fields that you can enable based on your need like Text field, Date field, and Dropdown List also you can enable multiple text fields and date fields based on your need

Example: On a sale invoice there is 6 Text field, 3 Date field, and 1 Dropdown field

Same way you can create custom fields for other document types like Delivery Challan, Quotation, Proforma, Purchase Order, Purchase Invoice, Credit Note, Debit Note, Multi Currency Invoice, Payment Receipt and Customer / Vendor.