Answered on September 13,2019
1) IDV value is not used to calculate the road tax. Invoice Amount of vehicle is used to calculate the road tax. I will take a guess on the road tax, but it might not be correct.
In Maharashtra, Petrol cars have 11-13% road tax and diesel cars have 13-15% road tax. I am assuming a road tax of 13% and depreciation of 30% on the price of vehicle as it is 5 years old. So, for a vehicle of 1 lakh, road tax will be 1 * (1-30%) * 13% = 9100 + taxes
It might be lesser than this as well. Please check with an agent as well.
2) Paying road tax doesn't mean you can use KA number plate in Maharashtra. If you are planning to stay in Maharashtra for more than a year, you should apply for MH registration.
3) Getting tax refund is a long process. It might take up to 1 year. You can check the status of road tax refund during this period by filing RTI.
Full tax amount will not be refunded. Assume that you have paid road tax as 100 in Karnataka at the time of registration and you have used it for 5 years there. As lifetime of a vehicle is 15 years, you will get extra tax paid for 10 years. So you will get 100*(10/15)= 66 or something in that range.
Also, please note that either the vehicle has to be mandatory registered in new state or the Old Registration has to be applied for cancellation, post which only the refund application will be accepted for payment of Pro Rata Tax Amount
Answered on November 11,2019
You can check this video to calculate the road tax to be paid in Bangalore.