Which assertion relates to completeness in financial reporting?

The assertion that relates to completeness in financial reporting is that all transactions are recorded. Completeness is a fundamental assertion in auditing, which ensures that all financial transactions that should be included in the financial statements are indeed recorded and reported. This assertion is critical because any missing transactions could lead to significant misstatements in the financial statements, impacting the overall reliability and integrity of the reported financial position and performance of the entity.

In the context of auditing, ensuring completeness involves verifying that all income, expenses, assets, and liabilities that should be reflected in the financial statements are properly included. This assertion helps auditors confirm that the financial information presented does not omit important transactions that could influence users' decision-making.

The other choices address different assertions: valuing transactions correctly pertains to accuracy, being free from errors relates to the assertion of presentation and disclosure, while appropriate disclosure of assets and liabilities aligns with the assertion of classification. Thus, the focus on transaction recording is what distinctly ties to the completeness assertion.