Voucher is known as the evident for the support of a transaction in the books of account. It may be bill, receipts, requisition form, agreement, decision, bank paying slip etc.

The act of examining documentary evidence in order to ascertain the accuracy of entries in the account books is called "Vouching". Vouching is a technical term which refers to the inspection by the auditor of documentary evidence supporting and substantiating a transaction. Simply stated, vouching means a careful examination of all original evidence i.e invoices, statements, receipts, correspondence, minutes and contracts etc. with a view to ascertain the accuracy of the entries in the books of accounts and also to find out, as far as possible, that no entries have been omitted in the books of accounts. Therefore, vouching is the act of testing the truth of entries appearing in the primary books of accounts. It is initial for auditing.