Four BIK tax traps that look like sensible choices — and the smarter alternatives that could save you thousands in Benefit-in-Kind tax.

If you’re choosing a company car, the monthly finance figure is the easy bit. The number most people overlook? The tax bill that lands quietly every year simply because you’re driving it.

HMRC calculates your company car tax using two things: the car’s official list price and its CO2 emissions. A car that seems like great value on a lease deal can turn into an expensive mistake if its emissions push it into a high tax band.

Here are four common traps — and what you could drive instead.

Trap 1: The Diesel Executive Saloon

You want something professional, comfortable, and badge-appropriate for client meetings. A diesel BMW 3 Series or Audi A5 fits the brief perfectly. List price around £42,000 — reasonable for a premium saloon. What’s the problem?

The numbers:

The diesel costs over £370 more every month in tax alone. That’s before you compare fuel, servicing, or anything else. Over a three-year lease, you’d hand HMRC an extra £13,500 — for a car that costs £3,000 less on paper.

And if that diesel doesn’t meet the RDE2 emissions standard? Add another 4% to the BIK rate. Your monthly tax jumps above £490.

The smarter move: The Tesla Model 3 isn’t the only option. A BMW i4 eDrive40 (from £52,000, 4% BIK) keeps you in a BMW while cutting your tax bill by nearly £5,000 a year. The Polestar 2 or Mercedes CLA EV also sit at 4% and cost less than their petrol equivalents once tax is factored in.

Trap 2: The PHEV With a Tiny Battery

Plug-in hybrids sound like the best of both worlds: electric for the commute, petrol for the long run. And some deliver exactly that. But not all PHEVs are equal when it comes to tax.

HMRC groups PHEVs by how far they can travel on electric power alone. The shorter the range, the higher your tax rate:

The numbers:

The PHEV costs four times as much in tax — and costs £5,000 more to buy. You’re paying a premium for a smaller battery, a shorter electric range, and a much bigger tax bill.

The PHEV trap gets worse from April 2028, when most 1-50g/km PHEVs jump to an 18% BIK rate regardless of electric range. That same £38,000 PHEV would cost a 40% taxpayer £2,736 a year — £228 a month — from 2028. A full EV would still be at 7%, or £1,064 a year.

If you’re signing a three or four-year lease today, that 2028 jump will hit before your contract ends.

The smarter move: Before you commit to a PHEV, check its official electric range. If it’s under 40 miles, you’re paying a tax premium for a token amount of electric driving. A full EV like the Kia EV3, Skoda Elroq, or Renault Scenic E-Tech gives you proper electric range, a 4% BIK rate, and no fuel costs for daily driving.

Trap 3: The Diesel That Fails RDE2

Not all diesels are taxed equally. HMRC applies a 4% surcharge to diesel cars that don’t meet the RDE2 (Real Driving Emissions 2) standard. RDE2 is the stricter, real-world emissions test introduced in 2021. Many diesels sold before 2021 — and some newer models still coming through — don’t meet it.

The difference is brutal:

That extra £37 a month might not sound disastrous on its own. But combined with the already-high BIK rates for diesel, it makes a petrol, hybrid, or electric alternative look increasingly compelling.

The RDE2 check: Your dealer should be able to confirm whether a diesel meets RDE2. If they can’t — or if the answer is no — walk away, or at least run the numbers against a petrol or electric equivalent.

The smarter move: A Volkswagen Golf-sized EV like the Cupra Born or MG4 sits at 4% BIK and costs a 40% taxpayer roughly £35–45 a month in tax. Even a mild-hybrid petrol can cut your BIK by 8–10 percentage points compared to a non-RDE2 diesel.

Trap 4: The “Bargain” Performance Saloon

A fast saloon for under £55,000 feels like a lot of car for the money. And on a straight PCP quote, it might genuinely look affordable. The trap? HMRC doesn’t care how good the deal was — it taxes you on the full list price, multiplied by the CO2 band.

Performance models produce a lot of CO2. That puts them in the very top BIK band: 37%.

The numbers:

The i4 costs £9,000 more to buy — yet saves you nearly £7,000 a year in tax. After year one, you’re already ahead. Over three years, the petrol car costs £21,000 more in tax than the electric one. And that’s before fuel.

The same maths applies across the board. An Audi S4 vs an Audi A6 e-tron. A Mercedes-AMG C43 vs a Mercedes EQE. The pattern is the same: the faster petrol car has a lower sticker price but a tax bill that destroys the saving within months.

The smarter move: Electric performance cars are genuinely quick — the i4 M50 does 0-62mph in 3.9 seconds — but sit in the lowest tax band. If you want pace and presence, the EVs deliver both for a fraction of the annual tax cost. Even a standard-range EV with strong acceleration (like a Tesla Model 3 Performance) gives you the speed without the tax hangover.

The Quick BIK Trap Checklist

Before you sign for any company car, ask:

• What’s the CO2 figure? Anything over 50g/km and you’re in double-digit BIK. Over 100g/km? Triple digits.
• Is it diesel? If so, does it meet RDE2? If not, add 4% to the BIK rate.
• If it’s a PHEV, what’s the real electric range? Under 40 miles means you’re paying 14%+ BIK for a car that’ll barely do the school run on battery.
• What’s the list price — not the discounted figure? HMRC uses the full P11D value, not what you negotiated. A big discount is great for the monthly payment, but irrelevant for the tax.
• What happens in 2028? If you’re leasing for 3–4 years, check where the BIK rates go. PHEVs face a steep climb from April 2028.

Why This Matters More Than You Think

BIK tax isn’t deducted from your payslip with a fanfare. It just quietly reduces your take-home pay every month. Most professionals don’t add it up annually — they just notice their net pay is a bit lighter than expected.

But over a typical three-year lease, the difference between a car at 4% BIK and one at 32% BIK can run well past £15,000 in personal tax. That’s the cost of a family holiday. Or a year of school fees. Or a deposit on a buy-to-let.

Choosing the right car isn’t just about the monthly lease figure. It’s about the total amount that leaves your pocket — including the cheque you’re writing to HMRC.

And if the tax maths feels like hard work? That’s exactly what a good broker handles. They know which cars sit in which bands, which PHEVs actually deliver useful electric range, and where the real-world deals live. You focus on what the car does for your business — they make sure the numbers add up.

This article reflects 2026/27 tax year rates as confirmed by HMRC. Vehicle prices and CO2 figures are based on manufacturer data and may vary by specification. This does not constitute financial advice — always confirm figures with your accountant. Tax treatment depends on individual circumstances and may change.

This article reflects 2026/27 tax year rates as confirmed by HMRC. It does not constitute financial advice — always confirm figures with your accountant before making a commitment.