This applies whether you buy cash or on credit - i.e. whether the payment is made on purchase or later.
Thus, a receipt, a copy of a cheque, etc. will not qualify for a voucher of a purchase transaction. It must be a bill - a so-called invoice, and it must be the original document, not a copy.
The reason for the requirement of an original invoice as documentation for expenses or purchase of goods, is, that usually there will only be one single original.
It is easy to make numerous copies of the same invoice. So, using only original invoice as a voucher for a purchase transaction you make sure that the transaction is only entered once into the accounts.
Of course you may risk losing the original invoice for which reason you will have to obtain a copy and use that for a voucher of the purchase transaction for the bookkeeping.
A typical mistake in such cases is that the original invoice had actually
already been entered, and by using a copy you thus end up having entered the
same purchase transaction twice.
- Go to next business issue: Sales Transaction Voucher