What is the amount involved. ? Have you evaluated taking a refund for fy 1920 by way of rectification and paying self assessment tax in fy 2021 if the client has spare funds.?
Try fy 1920 rectification, you might received the refund in a month and then you can use the same funds to pay fy 2021 sa tax before return filing due date.
ofcourse going to the officer is advisable provided he does the changes really fast