The tax paying documents have been prescribed under Rule 36 of the CGST Rules.
The ITC shall be availed by a registered person [including the Input Service Distributor (ISD)] on the basis of any of the following documents:
An invoice issued by supplier of goods or services or both;
An invoice raised by the recipient in case of inward supplies from unregistered persons or reverse charge mechanism supplies, subject to payment of tax;
A debit note issued by a supplier of goods or services or both;
A bill of entry or any similar document prescribed under the Customs Act, 1962 or Rules made there under for the assessment of integrated tax on imports;
An Input Service Distributor (ISD) Invoice or ISD Credit Note or any other
document issued by an Input Service Distributor for distribution of credit.
(ICAI FAQ PUBLICATION 06-09-2017 INPUT TAX CREDIT: FAQ NO.5)