In the UK, a tax easement designed to shield company car drivers of PHEVs from sharp hikes in payments is, as Autocar reports, unexpectedly opening a loophole for the most expensive and highest-emitting plug-in hybrids. The shift to the Euro 6e-bis standard is to blame: its revised CO2 methodology assumes a smaller share of electric-only driving, so many PHEVs see their official emissions rise when retested without any hardware changes.

That matters in Britain, where low CO2 ratings have made PHEVs a staple of corporate fleets and benefit-in-kind rates are tightly banded. Tip a model past 50 g/km and it can drop into a higher tax class. For example, the Vauxhall Astra PHEV moves from 30 to 51 g/km under Euro 6e-bis, which noticeably increases BIK over a typical three-year contract.

To soften the blow, the Treasury in the summer allowed a temporary reversion to the old test methodology or the continued use of previous figures, keeping the advantages in place until 5 April 2028. However, the Budget tweak changes how it works: if a Euro 6e-bis-compliant PHEV registered after 1 January 2025 has at least 2 km of electric range yet shows more than 50 g/km, it may be assigned a nominal 1 g/km. That, in turn, lets it slip into a gentler BIK band as though it were genuinely low-emission. The twist could skew fleet choices toward pricey, high-emitting plug-ins that qualify on a technicality, rather than encouraging the most efficient options.