Use the word Ltd. or Pvt ltd.

You cannot use them unless it is incorporated.

First incorporated than use .

 without incorporation the company does not come into existence hence cannot use PVT LTD or LTD which indicates the nature of company ie whether private or public

Befor its incorporation, business organisation can not use the word ltd. or pvt. ltd.

A limited liability company having formed as pvt. ltd. criteria can use the word pvt. ltd. and having criteria of  public limiled company all u/s. 3 of the companies act.,1956, only after it gets duly registered wih the Registrar of Companies, of the state in which its registered office is located.