If turnover is 3.5 Crore & file IT return by showing more than 6% profit as all transactions are through bank only. Under which section I have to file my IT return ?

Reply: Under section 44AB every person carrying on business shall, if his total sales, turnover or gross receipts, as the case may be, in business exceed or exceeds one crore rupees in any previous year. Provided that in the case of a person whose––(a) aggregate of all amounts received including amount received for sales, turnover or gross receipts during the previous year, in cash, does not exceed five per cent. of the said amount; and (b) aggregate of all payments made including amount incurred for expenditure, in cash, during the previous year does not exceed five per cent. of the said payment, this clause shall have effect as if for the words “one crore rupees”, the words “five crore rupees” had been substituted get his accounts of such previous year audited by an accountant before the specified date and furnish by that date the report of such audit in the prescribed form duly signed and verified by such accountant and setting forth such particulars as may be prescribed.

Provided that this section shall not apply to the person, who declares profits and gains for the previous year in accordance with the provisions of sub-section (1) of section 44AD and his total sales, turnover or gross receipts, as the case may be, in business does not exceed two crore rupees in such previous year.

Since you are not covered u/s 44AB, you are required to file return u/s 139 and required to maintain proper books of accounts and profit as per books of accounts is required to be shown in the return of income. Provisions of section 44AD are also not applicable on you since your turnover exceed Rs. 2 crore.