Builder delaying in sharing noc/possession letter

Dear Sir, We got a sort of letter from builder where its mentioned that we are taking house for furniture work only back in 2013 but till date he is delaying to share our NOC/Possession letter of our house. In our building there are almost 54 rooms and for everyone had same issue, but due to lots of other constraints people started staying. There are 2 other building in the same complex and our is last and 3rd one (as it was last to be constructed). For first 2, everyone got NOC earlier. Back in 2014, Builder formed the society also we all raised a voice that first provide the NOC for 3rd building and then you can form the society. But despite of any voices being raised, he formed Society (all 3 building) and now although we keep on following up for our Possession/NOC letter for our houses, he keep on delaying --that it will be done, don't worry. I understand without possession/NOC letter we cannot occupy the house, but since there was a lot of delay so everyone now had occupied the house. Pl suggest what need to be done. We all are ready to pay normal property tax as we are afraid that due to delay in Possession/NOC letter from builder, we should not be binded with any penalty, but don't what to do? Pl suggest the best way as we are not sure when the builder will provide the NOC/Possession letter to us?