I don't see the Customer PAN number in the invoice even though the same is added in the customer details. How to enable that?

Allow me to join you here and help to make sure the customer's PAN are shown in your invoices, deepak-singh.

At the moment, only the customer's email address, shipping, and billing address will show up when creating an invoice. Although, you can customize your invoice template and add a custom field for the customer's PAN. 

Here's how:

1. Go to the Gear icon and select Custom form styles.
2. Click New style and select Invoice.
3. Proceed to the Content tab, then click the header section of the invoice in the right-hand side.
4. Scroll-down to the Custom fields section, then click Manage custom fields.
5. Click Add field.
6. Type in the name of the field such as "Customer PAN", then check the box for All Sales form. 
7. You can also turn on the Print on form by sliding the bar to the right. This will include the customized field in the printed version of the invoice.
8. Click Save.

Please note that you need to manually type in the number when creating an invoice since this is a customized field. Let me give you this article to see more details about this feature: How to Add Custom Fields to Sales Forms and Purchase Orders.

I'd also like to share these articles for more references when customising your sales transactions: 

• Customise Invoices, Estimates, and Sales Receipts in QuickBooks Online
• Add, Customise, or Remove Logos on Sales Forms

Don't hesitate to always ask questions if you need more help from us. We're always here to guide and assist you all the time.