what is the period for Input Tax credit can be availed from date of purchase bill

Upto 1 year from the date of invoice

Earlier of 

1 Annual return filing date

2 Return filing date for September of the following FY

However, in cases of credit in special circumstances like new registration, voluntaryregistration, etc. the credit will not be available after the expiry of one year from the date of issue of tax invoice.

ITC can be claimed only within one year from the date of issue of tax invoice relating to supply. In any other case, the last date to claim ITC is earlier of the two below:

Before the filing of valid return for the month of September following the end of FY to which such invoice is related, or Before the filing of the annual return

Note: As per section 44, the last date for filing of annual return is 31st December following the end of the financial year.