Sales Invoice TIN Number

I want to show both the TIN Numbers mine as well as Customer’s on Sales Invoice

Yours you can setup letterheads

and for customer’s TIN no, you have to add custom feild. Check https://frappe.io/kb/customization/fetch-custom-field-value-from-master-to-all-related-transactions

That can only be seen on forms, I want the same to be shown on Invoicing Printing Report.