A source document is the original paper or electronic record that provides evidence that a transaction occurred and supplies the details needed to make an entry in the books of account. Common source documents include invoices, debit notes, and credit notes, each of which is generated at the point a transaction takes place.
A debit note is issued, typically by a buyer to a supplier, to record that goods have been returned or an amount owed should be increased. A sales invoice is issued to a customer to evidence a credit sale and states what is owed. A credit note is issued to reduce an amount owed, most often when goods are returned or an overcharge is corrected. Each of these documents is created outside the accounting books themselves, to record the details of a specific transaction as it happens.
The journal proper, however, is not a document at all; it is a book of prime entry used to record transactions that do not belong in any of the other specialised daybooks, such as the correction of errors, the writing off of bad debts, or opening entries when a business starts. It is prepared from other evidence, such as narrations and supporting calculations, rather than being itself a piece of evidence generated by an external transaction.
Examination tip: distinguish source documents, which are the raw evidence of a transaction, from books of prime entry, such as the journal proper, which record and summarise that evidence.