Understanding Source Documents in Accounting

1. Invoices

Invoices are perhaps the most common source documents. They are used in two ways:

• Sales Invoices: Issued by the business to a customer when goods or services are provided on credit. This tells the business that money is owed to them.
• Purchase Invoices: Received by the business from a supplier. This tells the business that they owe money to someone else.

2. Receipts

While an invoice is a request for payment or a record of a sale on credit, a receipt is proof that payment has actually been made or received. If you buy a coffee and the barista hands you a slip of paper, that is a receipt. In accounting, receipts are vital for verifying cash outflows and inflows.

3. Credit Notes

Sometimes, a transaction needs to be reversed or adjusted. If a customer returns faulty goods, the seller issues a credit note. This document reduces the amount the customer owes and serves as the source document for recording the return in the accounting books.

4. Bank Statements

A bank statement is a summary of all transactions occurring in a business's bank account over a specific period. It serves as a powerful source document for verifying cash balances and identifying bank fees or interest earned that might not have been recorded manually.

5. Purchase Orders (PO)

A purchase order is a document sent by a buyer to a seller indicating types, quantities, and agreed prices for products or services. While a PO itself isn't always the final trigger for a journal entry, it is a critical piece of evidence used to verify that an invoice is legitimate and matches what was originally ordered.

The Workflow: From Document to Journal

To understand how these documents function in a real business cycle, let's look at the flow of information. The process follows a strict hierarchy:

1. The Event: A transaction occurs (e.g., a customer buys a laptop).
2. The Source Document: An invoice is generated.
3. The Journal: The information from the invoice is recorded in a journal (the book of original entry).
4. The Ledger: The journal entries are posted to the relevant accounts in the ledger.

Worked Example: The Sales Transaction

Imagine "TechFlow Solutions" sells a software subscription to a client for $1,200 on credit.

• Step 1 (The Document): TechFlow generates Invoice #101 for $1,200. This document contains the date, the client's name, the description of the software, and the total amount.
• Step 2 (The Journal): The accountant looks at Invoice #101 and enters it into the Sales Journal.
• Step 3 (The Entry): The accounting entry would look like this: $\begin{aligned} \text{Accounts Receivable} & = \$1,200 \\ \text{Sales Revenue} & = \$1,200 \end{aligned}$
• Step 4 (Verification): Six months later, if the client disputes the charge, TechFlow pulls up Invoice #101 to prove the sale occurred.

Why Accuracy Matters

If a source document is lost, incorrect, or forged, the entire accounting system fails.

• Inaccurate Amounts: If an invoice for $1,050 is accidentally recorded as $1,500, the profit will be overstated, leading to incorrect tax filings.
• Missing Documents: If a business loses its receipts for fuel, it cannot claim those expenses, meaning it will pay more in taxes than it legally should.
• Fraud Prevention: Requiring a physical or digital source document for every entry prevents employees from creating "ghost" expenses to steal money from the company.

Exam Tip: Distinguishing Invoices from Receipts On exams, pay close attention to the timing. If the question mentions "goods sold on credit," look for an invoice. If the question mentions "payment received" or "cash paid," look for a receipt.

Summary Table of Source Documents

By mastering the identification and use of source documents, you ensure that the financial story told by the books is rooted in reality.