See the ZZZZ Best Company, Inc. case for this question.

Professional auditing standards identify the principal "management assertions" that underlie a set of financial statements. The occurrence assertion was particularly critical for ZZZZ Best's insurance restoration contracts. ZZZZ Best's auditors obtained third-party confirmations to support the contracts, reviewed available documentation, performed analytical procedures to evaluate the reasonableness of the revenues recorded on the contracts, and visited selected restoration sites. Comment on the limitations of the evidence that these procedures provide with regard to the management assertion of occurrence.