Fixed Deposit interst income - GST Applicable

Dear Sir.

 Greetings.  I am Muthaiah Jeyachandran From Tamilnadu.  I have a query. My firm have many Fixed Deposits with Bank. Every year bank pays our Firm Interest For Fixed Deposit.  The FD Interest Calculated as a Indirect Income.  in this, While Auditing GSTR-9, 9C For Fy : 2020-21, The Audit Executive Says,  The Fixed Deposit Interest is also GST Applicable.   If its Correcet how do for Last Year Interest GST in Current Year.

Please any one clear the issue.

Thanking You,

Muthaiah Jeyachandran.