GST CONTRACTOR

In one case of contractor in he not filed sales. He have filed only purchase in 3B and not sale. He is under assumption that there is chance of correction in Annual return and also not shown in Sept return. Only GSTR 1 of March is pending as he missed to file. Can we give details of sales in GSTR 1 of March as we have not filed GSTR 1 yet or any option in Annual Return. Or any better option?