Mandatory income tax return filing requires reporting advance tax and completing statutory self assessment to enable reconciliation and refunds. Filing an income-tax return is mandatory when an individual's gross income exceeds the exemption limit or when specified transactional or receipt thresholds are met; returns must be filed even where advance taxes have been paid. Reporting advance taxes through the return constitutes statutory self-assessment, allows reconciliation with Form 26AS and third party records, and enables refund claims. Failure to file attracts penalty. Administrative notifications have expanded the categories of persons required to file by prescribing additional deposit, receipt, turnover and tax deduction conditions.