Hello,
VDA or Variable Dearness Allowance is a payment (part of the total wage) that VARIES with some Consumer Price Index (whatever the series) compiled by the Government of India (if I am right, by National Sample Survey). Special Allowance is in the nature of a Dearness Allowance only but is a term used in the Minimum Wages Act. This Special Allowance is statutorily a part of the Minimum Wage under the act and is linked to a particular series also stated under the said act. Because the different series of Cost of Living/Consumer Price Index and different linkages these may vary at different rates but in essence, these are identical being in the nature of a "payment to neutralize the rising costs." Without going into technicalities of the matter, I suppose this explanation would be adequate!
Regards,
Samvedan
November 20, 2011