Query with regard to bank loan to be written off

A loan worth Rs. 20 crore is now payable in 10 installments worth rs 50 lakh each. The remaining 15 crores are to be written off as liability no longer payable. the first EMi of 50 lakh is payable on 21.03.16, the last being payable on 21.12.16. Should the complete loan be written off in march itself since the settlement has been arrived at or it should be written off proportionately ? Also the bank has said if we do not write off complete 15 crores in march then we will have to pay 6 crores instead of 5. Please suggest the appropriate accounting treatment