Source documents are original records that provide evidence of a transaction or event, while supporting documents are additional records that provide further details or evidence to support the information contained in the source documents.

Source documents are the starting point of an accounting transaction or event. They are usually created at the time of the transaction or event and include documents such as invoices, receipts, purchase orders, sales orders, bank statements, and payroll records. These documents provide details about the transaction or event, such as the date, amount, parties involved, and description of the transaction.

Supporting documents, on the other hand, are not created at the time of the transaction or event but are added later to provide additional evidence or details. They include documents such as contracts, agreements, emails, memos, correspondence, and legal documents. These documents help to provide a complete picture of the transaction or event and may be used to verify or explain the information contained in the source documents.

In summary, source documents are original records created at the time of a transaction or event, while supporting documents are additional records added later to provide further evidence or details. Both types of documents are important for maintaining accurate and reliable financial records.