Sales tax

1. Sales tax is an indirect tax that is levied on sale of goods. Before VAT was implemented, sales tax was being levied on sale of goods
2. VAT was introduced in place of sales tax wherein tax is levied only on the value added during the transaction. That is under VAT regime, input tax on local purchases can be set off against output tax
3. CST is part of sales tax and is levied on interstate transaction (from one to another state). No option to set-off input tax against output tax.

See the link for more details: https://www.scribd.com/doc/39004111/Difference-Between-VAT-and-CST