Materiality Question

Can I ask a silly question, when determining materiality. For example, year end is Sept 20×5. Audit date being July 20×5. Am I performing the materiality benchmark on 20×5 accounts or 20×4 accounts. I assumed 20×5 as the audit has already been done on the previous year, and the whole point is to have a balanced comparative. Why sometimes in answers materiality has been performed against 20×4.