1) i presume you have taken possession of the flat .
2) your registered sale deed must b e containing provisions for payment of interest by builder for delay in delivery of possession .
3) issue legal notice to builder to pay interest for delay in delivery of possession by one year . also seek directions that builder should complete internal work s
4) you have not mentioned whether occupation certificate has been issued by muncipal corporation or not
5) OC is granted by corporation only after the work is completed .
6) you can also seek compensation from builder for mental torture you have undergone for delay in delivery of possession
7) builder can recover maintenance after possession is handed over to flat owners for payment of property tax and other amenities