MRP Based sale and purchase under VAT

sale will be taken as including vat                         

if in purchase bill vat is separately mentioned than ok othervise it would also be taken as inclusive vat.

rectify me if i am wrong          

Dear Sir,

My name is Ashwin and I had opened a computer sales and service concern in Taramani area.
So far I didn't make any sales.
I am going to apply for TIN and CST registration as soon as possible for that i need the office in which i have to apply for taramani region.

Another main doubt is before applying for TIN and CST is it possible for me to make sales.
Shall i purchase from some other dealer and sell it to consumers. If so what is the procedure ie, I can give the customer invoice without tax or with tax.

Kindly advice me regarding this. I am new to this one.

Awaiting for your reply.

Thanks
Ashwin