Since the Software is provided to a client, then VAT is applicable. But, there is a thresh hold limit to it, which in most of the states is Rs.10 Lakhs.
1. For the time being you may provide a bill mentioning your PAN.
2. No, other taxes. (if you prepare a software on behalf of the client and charge a service fee, then Service Tax is applicable)
3. The limit for registration is 9 Lakhs, and you need to start charging from 10 Lakhs.
Trust this clarifies your query.
Feel free to call / get back in case of further clarifications.
Rohit R Sharma
BCOM, ACA, LLB-GEN, CERT. FAFP