Variable DA is variable according to changes in the consumer price index. The base index will depend upon the industry and the settlement arrived at by the respective state's minimum wages committee. VDA will be calculated at the rate of every increase in the consumer price index over the base so fixed. Therefore, a reference to the CPI is required to pay VDA on a monthly basis. Normally, VDA is a component of minimum wage fixation. VDA of all the employees in a particular industry (say, plywood sector, coir sector, leather sector) will be one and the same irrespective of basis salary.
Fixed DA, on the other hand, is a fixed percentage of the basic salary. Therefore, higher the basic salary the higher will be the FDA. FDA need not necessarily be fixed for a long time. It will also be revised according to changes in the CPI but not frequently. The amount of FDA will not be uniform for all the employees but will depend upon the basic salary.
Regards,
Madhu.T.K