Mismatch report

our client is government contractor
As per 26AS pwd credited gross bill
is 1lakh again deduct tds 1000 but
in this bill include 12 percent gst as per books our sale is mismatch as per 26As which receipt shown income tax return as per books and 26AS gross recript thedifference shown income tax return
notice wii be raise after file the return reason for mismatch receipts
what to do? please suggest