Supplementary information is any information presented in addition to the financial statements that is not considered necessary to fairly present the financial statements. This information may be presented with the financial statements or in a separate document. It should be derived from, and directly related to, the underlying records used to prepare the financial statements. The supplementary information should also relate to the same period covered by the financial statements. An example of supplementary information is an expanded table containing the details for any line item in the financial statements. Thus, a breakdown of the cost of goods sold could be presented, or a breakdown of the components of the fixed assets line item.
When supplementary information is presented, the auditor's job is to determine whether the information is fairly stated in relation to the financial statements as a whole. This involves such tasks as making inquiries with management about the purpose of the supplementary information, understanding how the information was prepared, and reconciling it to the underlying records.