Core rule: a VAT-registered supplier must issue the prescribed tax invoice for a taxable supply. For input credit, the buyer needs eligible taxable-business use and the required supporting document. Merely paying a bill does not establish either condition.
A regular tax invoice identifies the supplier and buyer as required, their registration details, invoice number and date, the goods or services, taxable amount and VAT. Check it against the actual supply and the supplier's VAT status. Approved abbreviated invoices have separate rules.
Example: a PAN-only shop issues a NPR 10,000 bill without lawful VAT. The buyer cannot invent NPR 1,300 input credit or treat part of the NPR 10,000 as recoverable VAT.
Keep the invoice with delivery or service evidence and payment records. Missing documentation should be corrected with the supplier, not fabricated internally.