please clear me difference

gross sale include all sale....that is exempt sale, zero rated sale, and other exempt sale...

but taxable sale include only that sale which is taxable.....it does not include zero rated sale and exempt sale.

The difference is clearly visible if you compare the definitions given in the VAT Act concerned. In Section 2 which is the definition section, you can find the definitions of the "turnover" which is nothing but the Gross Turnover and if it is for the period of one accounting year, then it is called "Gross Annual Turnover". The definition of taxable turnover is also there.

But how to calculate the taxable turnover and the Gross Turnover could be seen in the Rules of the concerned State. Please refer Rule 3 which deals with  the calculations, exemptions and deductions. First calculate the Gross Turnover and then start deducting one by one to arrive at the Taxable Turnover.