Audit is applicable:
A] if your turnover crosses the threshold limit in the current year. (FY 2020-21) or;
B] if you are opting OUT of presumptive scheme in the current year(FY 2020-21) (meaning you had opted for presumptive scheme in the previous year) and your net FNO Income is less than 6%(meaning either in loss or in profits less than 6%) but total income is greater than basic exemption limit; then you have maintain books of accounts and get the AUDIT done [Tax Audit is applicable].
If both the above conditions are not applicable; you can declare the FNO Income under presumptive taxation scheme and file the returns.
In this case audit will be applicable only if you had opted for presumptive scheme in any of the previous 4 financial years and now you are opting out of presumptive scheme in the current year and your total income exceeds basic exemption limit.
Also, You can opt for presumptive taxation scheme declaring your profits as more than 6% of turnover if you are resident in India.