cash purchase limit

There is no limit on cash purchase as per GST law and there is no limit on maximum purchase/ year.

Section 40A(3)-Where the assessee incurs any expenditure in respect of which a payment or aggregate of payments made to a person in a day, otherwise than by an account payee cheque drawn on a bank or account payee bank draft, 18[or use of electronic clearing system through a bank account, exceeds ten thousand rupees,] no deduction shall be allowed in respect of such expenditure.

Section 269SS-No person shall take or accept from any other person (herein referred to as the depositor), any loan or deposit or any specified sum, otherwise than by an account payee cheque or account payee bank draft or use of electronic clearing system through a bank account, if,—

(a)  the amount of such loan or deposit or specified sum or the aggregate amount of such loan, deposit and specified sum; or

(b)  on the date of taking or accepting such loan or deposit or specified sum, any loan or deposit or specified sum taken or accepted earlier by such person from the depositor is remaining unpaid (whether repayment has fallen due or not), the amount or the aggregate amount remaining unpaid; or

(c)  the amount or the aggregate amount referred to in clause (a) together with the amount or the aggregate amount referred to in clause (b),

is twenty thousand rupees or more:

 "specified sum" means any sum of money receivable, whether as advance or otherwise, in relation to transfer of an immovable property, whether or not the transfer takes place.

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:

Thus it is advisable not to make payment of 10000 or more in cash in a single day to a single person for any purchase. This is as per Income Tax Act,1961. But there is no such provision in GST law regarding limit on cash purchase and maximum purchase.