Tax policy to sell t shirts online

You have to have a CST Number. I dont know whether TN VAT permits to sell outside state without registration. But inside the state you can sell upto 6 lacs turnover without any registration.

Does not matter whether pvt ltd or proprietorship. A pvt. ltd company cannot be closed easily and there are many laws which may be used against you by tax officers.

Remember that govt. does not help anyone. It is only interested in revenue collection.

Try proprietorship first. On success, change to pvt ltd.