Rcm had not payd

Yes you are liable to pay RCM with interest & you cannot claim ITC for the same.

pay in cash ledger & setoff by filing DRC 03

Itc on rcm can be paid is available to you. since you have not paid so time limit to claim itc provision will not apply so u can claim it as itc.

however interst is cost for you

@ CA Dhruva

As per Order 2/2018 Central Tax
The .last date to claim ITC for FY 2017-18 is 31/3/2019.
If you Read the Defination of INPUT TAX CREDIT provided, in Section 2(63) , means the Credit of "Input Tax" & if you refer the Definition of INPUT TAX under Section 2(62) , It includes the Credit of RCM also .

Hence Querist is liable deposit the RCM with interest but cannot claim ITC for the same .