Maintenance of books of accounts required when income or turnover exceeds threshold; audit obligation follows under law. An assessee must prepare and maintain books of account when income, gross turnover or receipts exceed prescribed thresholds; Section 44AA governs maintenance while Section 44AB governs audit. The rule distinguishes specified professions, non specified professions, businesses, and businesses covered by presumptive taxation schemes, with thresholds and scheme eligibility determining the extent of record keeping and whether audit obligations apply.