However, Euro 6e-bis would have left manufacturers either retesting vehicles using older rules for the UK market or losing some of their tax advantages.
For example, Euro 6e-bis pushes the Vauxhall Astra Sports Tourer GS PHEV from 30g/km to 51g/km CO2 with no other changes, nudging it from the 13% tax band up to 16%. That would raise a 20% income taxpayer’s BIK tax bill from £5019 to £8532 over a three-year period – a £3522 increase.
To avoid this, the Treasury announced an “easement” during the summer, enabling manufacturers to convert Euro 6e-bis CO2 figures back to older standards or continue using older data, keeping affected vehicles under the 50g/km threshold until 5 April 2028.
The Budget proposed a slightly different process, where Euro 6e-bis-compliant cars will get a nominal 1g/km CO2 emissions figure if they emit more than 50g/km, offer at least one mile of electric range and were registered since 1 January 2025.
For most vehicles, this has the same effect, because all PHEVs that emit between 1 and 50g/km are taxed based on their electric range, not their CO2 emissions. Cars registered before 5 April 2028 will continue to get the easement until 5 April 2031 under a transitional arrangement.
However, this creates a loophole, as it excludes only PHEVs tested to the outgoing standards. Those that already emit more than 50g/km CO2 could, once retested to Euro 6e-bis, get reclassified at 1g/km, qualify for the easement and fall into a much lower BIK tax band.
