Reverse charge input tax credit timing clarified for unregistered supplier invoices under APGST, with invoice year governing limitation. The time limit for availment of input tax credit under section 16(4) of the APGST Act, 2017, in respect of supplies received from unregistered persons and taxed under reverse charge mechanism, is linked to the financial year in which the recipient issues the invoice under section 31(3)(f). In such cases, the relevant year is the year of invoice issuance, subject to payment of tax and fulfilment of the conditions and restrictions under sections 16 and 17. Delayed issuance of the invoice may require payment of interest and may also attract penal action under section 122.