tds

I am a NRI and have bought an under construction apartment for the total cost of around Rs. 51 lakhs from a builder in 2014. I have paid multiple installments since 2014 without deducting TDS. Total amount of installments paid up till now is Rs 48 lakhs. The apartment is almost ready for possession and I am about to make the final payment and want to deduct the TDS now. I have the following questions: 1. Since I did not pay TDS on the installments since 2014, should I be paying interest and penalty on the unpaid TDS? If so, how is that calculated? And will this interest and penalty come out of my pocket (so I don’t deduct this from the payment which I made to the builder)? 2. As per my understanding, I have to deduct total TDS of 1% which is Rs 51000. So I should be paying Rs 50,49,000 in total to the builder. Is this correct? 3. Apart from the cost of the apartment, there are some more charges which the builder is asking at the time of possession (like escalation charge, additional compensation charge, labor welfare charge, etc.). Is TDS also calculated on these or just on the cost of the apartment? 4. The service tax which I have to pay to the builder, is that calculated on the total cost (51 lakhs) or on cost after deducting TDS (50,49,000)?