Dear Querist
Kindly note that by withholding the IGST amount your client is essentially violating provisions contained in second proviso to Section 16(2) of the CGST Act, 2017 which provides as follows:
"Provided further that where a recipient fails to pay to the supplier of goods or services or both, other than the supplies on which tax is payable on reverse charge basis, the amount towards the value of supply along with tax payable thereon within a period of one hundred and eighty days from the date of issue of invoice by the supplier, an amount equal to the input tax credit availed by the recipient shall be9[paid by him along with interest payable under section 50], in such manner as may be prescribed"
The only option available to your client is to pay the full amount to the supplier, avail ITC and intimate the jurisdictional Suptt. on the specific facts. Recent 2026 Tripura HC judgments are also in your client's favour - Sahil Enterprises, Malaya Rub-Tech Industries. You may go through the said judgments and accordingly compile a defence of your client's case.
There is also a provision in the GST portal to communicate with the supplier for non-upload of invoices. This option can also be explored.
The basic bedrock of GST enactments mandate the suppliers and recipients to function cohesively and seamlessly.