Input tax credit eligibility requires possession of a tax invoice, receipt of goods or services, tax payment, and return filing. Section 16 conditions input tax credit on possession of a tax invoice or prescribed document from a registered supplier, receipt of goods or services (including deemed receipt on delivery to a recipient or their direction), actual payment of the tax to the Government in cash or via permissible credit utilisation, and filing of the prescribed return; it excludes credit where depreciation on the tax component of capital goods has been claimed and requires reversal of credit where the recipient fails to pay the supplier within the statutory period, with restoration upon payment.