1% tds not deducted by bank or self

I bought a flat in Noida for 70 L. Out of this 80% was paid by bank and 15% has been paid by me. However, no tds has been deducted till now. What shall i do now? Shall i deduct tds on full 70L when i pay rest 5% or just on 5%. Also, is there any logal implication on me for not depositing the tax. Unfortunately, the customers are not educated enough and builders dont want to raise this point themselves. Please suggest