Please........... Don't get confused.
In this query the profit margin was more than 8% so the queriest wanted that extra margin to be adjusted against remuneration and finally pay 8% with books of accouts so that tax audit u/s. 44AB not mandatory. In case the remuneration is deducted more and the final taxable income reduced below 8%, tax audit becomes mandatory.
So, note that in both the schemes if profit margin is below 8%, tax audit triggers.
Only difference is under presumptive scheme deduction of remuneration & interest to partners is not allowed (from AY 2017-18), but in normal scheme it is allowed.
Now in your above referred example :
T/O - Rs. 50lakhs Profit 8% - 4lakhs _ next Remuneration - Rs. 3.30 lakhs Balance - Rs. 70000 Tax on 70000 * 30% = 21000 + cess... Is it correct way..
You are straight forward assuming 8% profit, (means u/s. 44AD); so after that remuneration cannot be deducted.
Otherwise, maintain books of accounts........ let the net profit actually be 70000/- as per books. That being less than 8% of TO....... triggers section 44AB........ so prepare Tax Audit report and submit with the said tax liability (and of course, penalty for late filling of tax audit report)