Procedure to cancel purchase of property already registered

Hi......on 8 th october i booked 1 bhk flat.till now i have paid 2.5lacs rs to builder including registration. due to lack of documentation { absence of commencement cert.} Bank delayed payment.builder techical team and bank team both have discussed and prob is solved.but this moment they dont have government approved layout and cc.so i want cancel this agreement to avoid problems in future.please advice how to cancel this deal with minimum loss