claim

CARRY FORWARD IT TO THE NEXT MONTH 

Please refer sec. 54 of CGST Act, 2017 which lists out two scenarios wherein you can claim refund of unutilised ITC.

One in case of zero rated supplies i.e. exports, supplies to SEZ unit/ developer

Second in case of inverted duty rate structure.

In all other cases, you cannot claim refund except when you shut down your business. C/f till next month where liability arises so that you can offset.