The registration number allotted to the dealers is popularly known as TIN i.e. Taxpayer Identification Number. This is a eleven digit number to be quoted in all VAT transactions and correspondence. (or)
The Tax Payer’s Identification Number (TIN) is new unique registration number that is used for identification of dealers registered under VAT. It consists of 11 digit numerals and will be unique throughout the country. First two characters will represent the State Code as used by the Union Ministry of Home Affairs. The set-up of the next nine characters may, however, be different in different States.
TIN is being used for identification of dealers in the same way like PAN is used for identification of assesses under Income Tax Act. All the dealers seeking for new registration under VAT or Central Sales Tax will be allotted new TIN as registration number, however every State Commercial Tax Department have made provisions to issue new TIN to their existing dealers replacing old registration/ CST number
so In brief there is no difference in VAT number,TIN or CST number ,now only one number is required for all type of sales i.e TIN it may be called VAT number as it is used intra state sales and may be called CST number as same is required for CST number .TIN is being issued to all new dealers whether required for intra or inter state sales but for old dealer (inter state) CST number will be changed with TIN in phased manner and method adopted by each state is different.

I have arranged a complete list of First Two digit of all the state and Union territories which is given here under.But I am arranging the detail of other 9 digits and publish the same in due course.One I can say that different rules are followed for rest of 9 digits in each states.If any body has a Information about these numbers in respect of their own state then kindly share with us in comment .
To know or to verify your TIN/VAT number Click link given in the name of each state.I will provide Link for all Tin verification site ASAP.