Gstr 2a

While finalising books of Accounts for FY 2017-18 , should we consider GSTR 2A . Also there is a provision to to reverse ITC before 30th september . So should we reverse ITC if it is not appearing in GSTR 2A. My point is that we have validly received goods or services and taken ITC in GSTR 3B now there is a need to check for GSTR 2A, if at all there is default then it is fault of supplier .