There in no provision in GST which restrict the cash sale transaction.
But Cash Transaction is restricted by Income Tax Act as below:-
Section 269ST :- No person shall receive an amount of two lakh rupees or more—
(a) in aggregate from a person in a day; or
(b) in respect of a single transaction; or
(c) in respect of transactions relating to one event or occasion from a person,
otherwise than by an account payee cheque or an account payee bank draft or use of electronic clearing system through a bank account:
Provided that the provisions of this section shall not apply to—
(i) any receipt by—
(b) any banking company, post office savings bank or co-operative bank;
(ii) transactions of the nature referred to in section 269SS;
(iii) such other persons or class of persons or receipts, which the Central Government may, by notification in the Official Gazette, specify.
Explanation.—For the purposes of this section,—
(a) “banking company” shall have the same meaning as assigned to it in clause (i) of the Explanation to section 269SS;
(b) “co-operative bank” shall have the same meaning as assigned to it in clause (ii) of the Explanation to section 269SS.’.
The CBDT has issued a press release dated 5th April 2017 by which it has provided important clarification regarding the restriction imposed on cash transaction by sections 269ST & 271DA inserted by the Finance Act 2017 to the Income-tax Act. The CBDT has clarified that the said cash transaction limit of Rs 2 lakh will not apply to withdrawal from banks, cooperative bank and post offices.
Section 40A(3):- Any expenditure in respect of which payment is made in sum exceeding rs.10,000/- in a single day to a single person otherwise than by an account payee cheque or an account payee bank draft or use of electronic clearing system through a bank account, shall not be allowed as deducation.