Input tax credit entitlement requires invoice, receipt, tax payment and timely return; non payment triggers reversal and interest. Registered persons may claim input tax credit for supplies used in business provided they hold a tax invoice or prescribed document, have received the goods or services (including deemed receipt), the tax on the supply has been paid to the Government in cash or by utilising admissible input credit, and they have furnished the required return. Credit for goods received in instalments is available only after the last instalment. Credit is barred where depreciation was claimed on the tax component of capital goods, is subject to a statutory time limit, and must be reversed with interest if the recipient fails to pay the supplier within the prescribed period.