Reverse ITC in the next return along with interest. Interest is to be paid from the date of taking ITC and till the date of reversal. See proviso to Section 16(2) of CGST Act, 2017 extracted below :-
"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 be added to his output tax liability, along with interest thereon, in such manner as may be prescribed :
Provided also that the recipient shall be entitled to avail of the credit of input tax on payment made by him of the amount towards the value of supply of goods or services or both along with tax payable thereon."