Simple query plz help

If CST is charged on purchase then it will be part oi the cost of the goods,

Only VAT credit on purchase is allowed to be set off...

On the other hand, VAT and CST charged on sale, becomes VAT and CST liability which can be set off against VAT credit {Vat paid at the time of purchase}

output vat is applicable on sales and input vat on purchase......cst is central sales tax....thats' why it is added in output vat and not in input vat