Vouching is a manual audit procedure where the auditor tests the validity of transactions or records by tracing them backward from the final records to the original source documents. This technique helps verify the authenticity and accuracy of the entries in the accounting records by ensuring that each entry is supported by proper documentation. For example, an auditor might start from an entry in the general ledger and trace it back to the original invoice or receipt to ensure its validity.
Reference:
IIA Global Technology Audit Guide (GTAG) on Understanding and Auditing Big Data IIA Standard 2310: Identifying Information