About TDS To advance payment

If you are purchasing materials against the advance payment, then no TDS deduction is necessary.

Many of the entries in  26AS statement for Contractors resemble advance payment (regarding R.A Bills)rather the final bill .  It is commonly seen in this Industry.

In general you have to make T.D.S since its the 'payment or credit which is earlier' at the time you make a payment and  after completion of contract or otherwise arriving at final bill, adjust the same.