From the 1st April 2020, a more accurate way of testing vehicle CO2 emissions will be introduced on all new vehicles.

HOW WILL THIS AFFECT YOUR ROAD TAX?

The new WLTP testing procedure has been designed to better reflect real driving conditions, to give a more accurate view of a vehicle’s emissions and fuel economy. This change takes effect from 1st April for VED (Vehicle Excise Duty or Road Tax) and 6th April for Benefit in Kind on Company Car Tax. Because the WLTP test is more stringent, the results are more realistic and this could mean an increase in road tax for your new car.

So if you're considering buying a new Citroen, doing so before 1st April 2020 could save you up to £685.