The mentioned contract is a Production contract and attracts TDS at 2% if the contract is with a company or 1% if it is with an HUF or an individual. Sales Tax (ST) is inclusive only of 194I rent payment; ST should be excluded. Therefore, deduct 2% on the principal amount + ST. ST registration and all details are the contractor's responsibility. If the contractor levies ST, deduct TDS along with the ST amount. If the contractor does not charge ST, then leave it and deduct only on the invoice amount. Basically, deduct based on the invoice value alone, but ensure that his PAN No. is mentioned on the invoice.
Regards,
Narayanan