Final answer:
An auditor may perform substantive tests before the balance sheet date when looking to roll forward data from an interim date, operating in predictable environments, or when there is a higher risk of material misstatement requiring more persuasive evidence.
Step-by-step explanation:
An auditor may perform substantive tests before the balance sheet date (BS date) under certain circumstances. One such circumstance is when the auditor wants to roll forward the financial data from an interim date to the balance sheet date in an efficient manner. This may be more practical when auditing a company with a high volume of transactions near year-end or if the auditor's workload is spread out. Another circumstance is when the company being audited operates in a predictable environment with consistent transaction patterns, allowing tests carried out earlier to be relevant at the balance sheet date. Additionally, performing substantive tests earlier may also be necessary when the auditor suspects there is a higher risk of material misstatement and needs to gather more persuasive audit evidence to mitigate this risk.