From 1 January 2026, the UK will adopt a new emissions testing standard – Euro 6e-bis – which could significantly impact the way plug-in hybrid vehicles (PHEVs) are taxed. Under the updated lab and real-world testing methods, many PHEVs are expected to see their official CO₂ figures rise above the key 50g/km and 75g/km thresholds.
This matters because both Benefit-in-Kind (BiK) and Vehicle Excise Duty (VED) are based on emissions. Higher readings will mean higher BiK percentages and VED costs. For example, a PHEV with a 50-mile electric range could move from 40g/km CO₂ (9% BiK, £110 VED) to 80g/km (22% BiK, £270 VED) under the new system.
Salary sacrifice schemes will also be affected, as only cars with emissions below 75g/km will remain eligible.
For fleets and drivers, the key message is: act early. Vehicles registered in late-2025 may be tested under the new standard, even before the 2026 deadline kicks in. That means Q4 2025 orders could be most at risk of higher tax bands. Fleets should check manufacturer emissions updates and order cut-offs to avoid unexpected cost hikes.