Add fields in tax invoice

Hello, @mohannad ebrahim. 

Yes, we can add fields in tax invoices by creating Custom fields in your sales forms. 

Please note that this feature is unavailable for Essentials. To use custom fields on purchase orders, you’ll first need to turn on the purchase orders setting. 

To add Custom fields, we have to: 

1. Go to Settings ⚙ and select Custom fields.
2. Choose Add field.
3. Enter a name in the Name field.
4. Select the All Sales forms or Purchase Order checkbox. Or, select both. 
5. (Optional) To show the custom field on printed and delivered forms, turn on Print on form. Otherwise, it’ll only appear in QuickBooks Online.
6. Click Save.

I'll add this guide for more info: Add custom fields to sales forms and purchase orders in QuickBooks Online. 

You can also check out this article about receiving and tracking customer remittances in QuickBooks Online: Record invoice payments in QuickBooks Online. 

The Community forum is available 24/7 to assist with any invoice-related concerns. Keep safe!