What are source documents in accounting?

A source document is the original written evidence of every business transaction, such as an invoice, receipt or cheque counterfoil. It is the starting point of the whole accounting process, because no entry should be made without a document to support it.

What is a source document?

A source document is the original record created when a transaction happens, and it holds key details such as the date, amount, parties involved and type of transaction. It becomes the "source" for all the accounting entries that follow, because the information in the journals and ledgers is taken straight from it. Without a source document, an accountant has no basis to record anything; every figure in the books can ultimately be traced back to a document that supports it.

Why they matter as evidence

The most important role of a source document is as evidence that a transaction did take place. It confirms the amount, the date and the parties involved, so the business records can be trusted and checked. When an auditor or owner wants to verify that an entry is correct, they refer back to its source document. These documents also matter when a dispute arises with a customer or supplier, because they form an objective written record of what was agreed and carried out.

Invoice

An invoice is issued when goods or services are sold on credit, meaning payment will be made later. It lists the goods sold, the quantity, the unit price, the total, and the names of the seller and buyer. For the seller, the invoice sent out is the basis for recording a credit sale; for the buyer, the invoice received is the basis for recording a credit purchase. Because it involves a credit transaction, an invoice is usually recorded in the sales journal or purchases journal, not the cash book.

Receipt

A receipt is proof that a payment has been received, and it is issued by the party receiving the money. It shows the date, the amount paid, and the purpose of the payment. Unlike an invoice, which relates to a credit transaction, a receipt confirms that an actual exchange of money has taken place, whether in cash or through the bank. For a business, a receipt it receives is proof of a payment made, while a copy of a receipt it issues supports the record of money received in the cash book.

Credit note

A credit note is issued by the seller to the buyer when the amount the buyer owes needs to be reduced, for example when goods are returned because they are faulty, or when there was an overcharge in the original invoice. It reduces the buyer's debt to the seller. For the seller, the credit note is the basis for recording sales returns; for the buyer, it is the basis for recording purchases returns. The colour red is traditionally associated with credit notes because it reduces the original amount.

Debit note

A debit note, by contrast, is used to add to the amount owing, or to tell another party that their account has been debited. It is often issued when a buyer was undercharged in the original invoice, or to accompany goods being returned to a supplier. Its function is the opposite of a credit note: one adds, the other reduces. Understanding the difference between these two notes matters, because students easily confuse who issues them and their effect on the debtor's or creditor's account.

Cheque counterfoil

A cheque counterfoil is the small part left in the cheque book after a cheque is torn out and given to the payee. It records the date, the amount, and to whom the cheque was written, so the business keeps a record of payments made by cheque. Because the actual cheque is handed to the payee, this counterfoil is the evidence that stays with the payer. It is used to record the payment in the bank column of the cash book, and later helps when preparing a bank reconciliation statement.

Payment voucher

A payment voucher is an internal document that supports and approves a payment before money is released. It usually lists the purpose of the payment, the amount, and the signature of the person approving it, and is attached to supporting documents such as an invoice or receipt. A payment voucher strengthens internal control because it ensures every payment is checked and approved by the right people, rather than paid out without checks. It helps prevent false payments and provides a clear audit trail.

How they flow into the books of prime entry

The basic flow is: source document to book of prime entry, then to the ledger, and finally to the trial balance. Each type of document flows into the appropriate book of prime entry: sales invoices into the sales journal, purchase invoices into the purchases journal, credit notes into the returns journals, and receipts and cheque counterfoils into the cash book. From the book of prime entry, the entries are posted to the ledger. Understanding this flow explains why the source document is the first step that cannot be skipped in the accounting cycle.

The information they contain

Although their layouts differ, most source documents contain the same core information: the transaction date, the names of the parties involved, a description of the goods or services, the amount of money, and often a serial number for reference. It is this information that is transferred into the accounting records. The reference number on each document lets an entry be traced back to its original document easily, making the checking and audit process faster and more reliable.

Common mistakes and good practice

Common mistakes include confusing an invoice with a receipt, or a credit note with a debit note, because students are unclear about who issues each document and its effect. Good practice is to keep every document in order, number them, and always match an entry to its supporting document. In an exam, understanding the purpose of each document matters more than memorising its name, because questions often ask students to identify the correct document for a transaction and the related book of prime entry.

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FAQ

What is the difference between an invoice and a receipt? An invoice is issued when a sale or purchase is made on credit and shows the amount to be paid later, whereas a receipt is issued after a payment has been received as proof that money has changed hands. One creates a debt while the other confirms its settlement, so the two should not be confused.

Who issues a credit note? A credit note is issued by the seller to the buyer to reduce the amount owing, usually when goods are returned because they are faulty or when there was an overcharge in the original invoice that needs correcting. The seller records it as a sales return, and the buyer as a purchases return.

Why must source documents be kept? They are evidence that each transaction did happen, they let entries be checked and audited with confidence, and they support the business if a dispute arises with a customer or supplier. Keeping them in an orderly, numbered file also lets any entry be traced back to its original document whenever it is needed.