F.y 20-21 audit limit

In case you do not opt for showing income u/s 44AD, then tax audit is not compulsory for you but is suggested to get tax audit done. And in case you had opted to income disclosure u/s 44AD, then tax audit is compulsory.

Audit under section 44AD is compulsory in your case as the NP is less than 6%. If you offer anything less than 6% and file return, immediately you get defective return notice under 139(9) for not attaching audit report as lesser income is offered.