sir, i have purchase a duplex in bhopal and registry for the same has been done, and loan is disburse from bank, for complete the balance amount i have given him post dated cheque and the entry of the cheque detail has been done in registry document.the cheque is valid for 3 months validity of cheque is expired and payment was not made. now builder is saying that registry has become null and void due to lack of payment.it is not my fault it is from builder side who did not present cheque in bank for encashment.Kindly suggest me now what to do next, is registry become null and void or not.