TDS

Sec 194J of Income Tax Act - "Any person, not being an individual or a Hindu undivided family, who is responsible for paying to a resident any sum by way of

(a) fees for professional services, or

(b) fees for technical services, [or]

[(c) royalty, or

(d) any sum referred to in clause (va) of Section 28

shall, at the time of credit of such sum to the account of the payee or at the time of payment thereof in cash or by issue of a cheque or draft or by any other mode, whichever is earlier, deduct an amount equal to [ten] per cent of such sum as income-tax on income comprised therein."

1. Sales order value is not reduced by TDS.

2. Yes, you need to collect TDS certificates from the clients.

3. In any case the company has to file its income tax return, then whatever tax liability is calculated is paid less TDS deducdted by clients.  So if one client has not deducted TDS, it is his headache and not yours.