The Source Document in an Accounting Transaction

The Key Information That Is Found in the Source Document

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Each time a company makes a financial transaction, some sort of paper trail is generated. That paper trail is called a source document. If a small business writes a check out of its checking account for office supplies, for example, the source documents are the check and the office supplies receipt.

Why Source Documents Are Important

The source document is essential to the bookkeeping and accounting process as it is the evidence that a financial transaction occurred.

If a company is audited, source documents back up the accounting journals and general ledger as an indisputable audit trail. 

Keeping a source document for a business is just like keeping receipts for tax-deductible items for your personal taxes. If your taxes are audited, they provide the proof that you've made those purchases. The same is true for your business, but in business, you don't keep receipts only for tax deductible expenses. You keep original documents for every financial transaction.

What Source Documents Provide

A source document describes all the basic facts of the transaction, such as the amount of the transaction, to whom the transaction was made, the purpose of the transaction, and the transaction date.

Here are a few examples of common source documents:

  • canceled check
  • invoice
  • cash register receipt
  • computer-generated receipt
  • credit memo for a customer refund
  • employee time card
  • deposit slip
  • purchase order

How to Treat Source Documents

The source document should be recorded in the appropriate accounting journal as soon as possible after the transaction. After recording, all source documents should be filed away in some sort of system where they can be retrieved if and when they are needed.

In certain instances, it may even be important to provide the chain of custody to be able to determine that the source document in question remained in your control.

Source Documents vs. Photocopies

In most circumstances, photocopies of source documents are legally acceptable. The Internal Revenue Service, for example, has accepted photocopies of receipts since 1997, so long as they are legible, contain all the information present in the original and, within the limits of the scanning process, present that information in a format identical to the original.

A materials receipt that specified the objects purchased and the price paid, but that was scanned without the name of the supplier would not qualify. A document that presented all the information in the original receipt, but that been retyped in Word or Excel format would also not qualify. 

The IRS standard —​ complete, legible and an accurate reproduction of the original —​ is the same standard used in many businesses and government agencies. Other institutions, however, add to these general requirements.

The University of Washington, for instance, only accepts as substitutes for the original document photocopies scanned at a minimum density of 300 dots per inch (dpi), and presented in either PDF or  TIFF formats; it does not accept JPEG photocopies.

If you are planning to scan accounting or legal documents to facilitate storage, check with the relevant institution to be sure they will accept the documents in the format you're planning to use.