Why is My Roadtax Store refunding the difference for my car's road tax?

There is a slight possibility that My Roadtax Store (MRTS) might call you so that we can provide a refund on road tax as there could be a slight discrepancy between the initial payment purchase and the payment requested by JPJ. This is solely because of the following:

• Differences in vehicle categorization offered by JPJ (saloon vs non-saloon)
• Differences in road tax cost for engine capacity (CC) for your car make and model.