27 December 2017
ITC is not allowed after any of the following happens due date of return for month of September of next financial year annual return filed for relevant year (Filing date, not due date)
28 December 2017
There is no time limit for utilisation of the ITC once availed the credit to Electronic Credit Ledger. Sec 16(4) applies for availment of input credit only, once availed to Electronic credit ledger within the time prescribed in Sec 16(4) you can utilise whenever you have the output liability.