1. when the assessments were made on introduction of the new capital value system of property tax calculation, the BMC had issued notice to the assessees requiring them to submit their objections against the calculation
2. since you have already paid the property tax, it will be deemed that you accepted the calculation of BMC as being correct
3. so now it will be very difficult to challenge
4. however you can file a RTI Application seeking details from BMC as to how it assessed the close verandah for property tax and under which rule.
5. At the highest your application may be rejected, but its worth giving a try so that if in case BMC does give any information about the mode of computation and if that appears to be arbitrary then you can challenge the same by filing a Writ Petition in High Court