Hi
TDS is not deducted either on Gross or on Net Salary
There are lots of considerations as Below
Full Basic+DA is Considered as Taxable Income
Conveyance Allowance is exempted upto 9600/- Per Annum
Medical Allowance is exempted upto 15000/- Per Annum
HRA is is exempted as actuals or 40% on Basic
other allowances are considered as Taxable income except washing, Food coupons & LTA
After there you should Deduct PT and if there is any other taxes on employee.
Later you should calculate the Deductions under Section 80 for PF, Housing Loan, Insurance and education fees
Based on those only you should deduct TDS