Bik Tax Calculator

Estimate your Benefit in Kind tax, annual taxable benefit, monthly personal tax cost, and optional fuel benefit tax for a UK company car.

Enter your vehicle and tax details

This calculator uses standard UK BIK percentage logic, including ultra-low emission bands for 1 to 50 g/km cars and a diesel supplement capped at 37%. Figures are estimates and should be checked against your payroll or tax adviser.

Your estimated result

Expert guide to using a BIK tax calculator in the UK

A BIK tax calculator helps drivers, employers, and finance teams estimate the tax cost of a company car. In the UK, BIK stands for Benefit in Kind. It applies when an employee receives a non-cash benefit through work, such as private use of a company vehicle. The value of that benefit is taxed through PAYE or self assessment, depending on the employee’s tax position and payroll setup.

For company cars, the key question is simple: how much taxable value does HMRC assign to the vehicle, and how much tax does the employee pay on that value? The answer depends on several inputs, including the car’s P11D value, fuel type, CO2 emissions, electric-only range for certain low-emission vehicles, and the employee’s income tax band. If an employer also pays for private fuel, an extra fuel benefit charge can apply, which can materially increase the employee’s tax bill.

A practical way to think about BIK is this: the taxable value is not the same as the amount of tax you pay. First, HMRC determines the taxable benefit. Then your income tax rate is applied to that taxable amount.

How a BIK tax calculation works

The core formula behind a BIK tax calculator is straightforward:

1. Start with the car’s list price, often referred to as the P11D value.
2. Subtract any qualifying employee capital contribution, subject to HMRC limits.
3. Apply the relevant BIK percentage for the tax year and vehicle type.
4. Multiply the resulting taxable benefit by the employee’s income tax rate.

For example, if a company car has a taxable value of £10,000 and the employee is a 40% taxpayer, the annual BIK tax would be £4,000. If private fuel is also provided, a separate fuel benefit multiplier is used, and the same BIK percentage is applied to that multiplier. That can significantly increase the total annual tax cost.

What affects BIK rates the most

• CO2 emissions: Higher emissions usually mean a higher BIK percentage.
• Fuel type: Diesel cars can attract a diesel supplement, subject to the overall cap.
• Electric-only range: For cars emitting 1 to 50 g/km, longer electric range usually reduces the percentage.
• Tax year: BIK percentages can change from one year to the next, so planning ahead matters.
• Income tax band: A 20% taxpayer and a 40% taxpayer can face very different net costs for the same vehicle.

Why electric vehicles usually look attractive in a BIK calculator

Fully electric company cars have been especially attractive in recent tax years because the BIK percentage has remained very low compared with petrol and diesel alternatives. Even when EV list prices are higher, the very low percentage can produce a lower personal tax bill than a cheaper petrol car with moderate CO2 emissions. That is one reason many salary sacrifice and company car schemes have shifted strongly toward EVs.

However, low BIK alone does not guarantee the best overall outcome. Drivers should also consider monthly lease cost, charging setup, public charging availability, mileage profile, insurance, and whether the employer provides home charging support. A good BIK tax calculator gives an immediate tax estimate, but a complete decision should also include total running cost and practicality.

Real UK BIK comparison data

The table below summarises headline company car tax percentages for selected low-emission scenarios using published multi-year policy rates. These percentages show why tax planning over several years can matter for fleet decisions.

Vehicle scenario	2024/25	2025/26	2026/27	2027/28
Fully electric, 0 g/km	2%	3%	4%	5%
1 to 50 g/km, electric range over 130 miles	2%	3%	4%	5%
1 to 50 g/km, electric range 70 to 129 miles	5%	6%	7%	8%
1 to 50 g/km, electric range 40 to 69 miles	8%	9%	10%	11%
1 to 50 g/km, electric range 30 to 39 miles	12%	13%	14%	15%
1 to 50 g/km, electric range under 30 miles	14%	15%	16%	17%

For mainstream combustion cars, the percentage rises progressively with emissions. A petrol or diesel car around 100 to 120 g/km can sit in a much higher band than an EV or long-range plug-in hybrid. As emissions rise, BIK can move quickly toward the upper part of the scale, with an overall cap of 37%.

Fuel benefit, often the hidden cost

Many drivers focus only on the vehicle benefit and overlook fuel benefit tax. If your employer pays for private fuel, HMRC uses a set fuel benefit multiplier. The car’s BIK percentage is then applied to that multiplier, and your tax rate is applied to the result. For many employees, this can mean the tax cost of free private fuel is higher than the real value they receive, especially if private mileage is modest.

This is why a good BIK tax calculator should let you compare the result with and without private fuel. In many cases, reimbursing private fuel yourself may be financially better than accepting an employer-funded fuel card for unrestricted private use.

Tax year	Fuel benefit multiplier	Fully electric BIK rate	Top standard BIK cap
2024/25	£27,800	2%	37%
2025/26	£28,200	3%	37%
2026/27	£28,600	4%	37%
2027/28	£28,900	5%	37%

What the P11D value means

The P11D value is normally the list price of the car plus accessories and VAT, before first registration fee and Vehicle Excise Duty. This is important because BIK is not based on what your employer paid after fleet discount. It is based on the tax value set by HMRC rules. If a car has factory options that increase list price, they can also increase the BIK charge.

Some employees make a capital contribution toward the car. In qualifying cases, that can reduce the taxable value used for the calculation, subject to HMRC limits. If you are comparing vehicles, make sure the P11D values are consistent, otherwise the comparison may be misleading.

Understanding plug-in hybrid outcomes

Plug-in hybrids can look very efficient in a brochure, but their BIK outcome depends heavily on electric-only range. Two cars with the same CO2 band can have different tax percentages if one can travel much farther on electric power alone. That is why many BIK calculators ask for electric range when emissions are between 1 and 50 g/km.

In real-world use, a plug-in hybrid can still be expensive if it is rarely charged. From a tax perspective, it may sit in a favourable band. From a running-cost perspective, however, the advantage can disappear if the car is used mostly as a conventional petrol vehicle. Businesses should therefore combine tax analysis with actual usage data.

Who should use a BIK tax calculator

• Employees choosing between a cash allowance and a company car.
• Drivers comparing EV, hybrid, petrol, and diesel models.
• Employers designing car policies or salary sacrifice schemes.
• Fleet managers projecting total reward cost over several tax years.
• Accountants and payroll teams validating expected employee tax deductions.

Common mistakes when estimating BIK

1. Using the discounted purchase price instead of the P11D list price.
2. Ignoring private fuel benefit.
3. Choosing the wrong tax year.
4. Forgetting the diesel supplement where relevant.
5. Assuming all hybrids have low BIK without checking electric range.
6. Comparing annual tax only, rather than monthly impact and total package cost.

BIK versus a car allowance

A car allowance gives employees more freedom, but it also pushes cost and risk onto the driver. Insurance, depreciation, servicing, and financing may all become the employee’s responsibility. A company car can be simpler, especially for high-mileage drivers or those wanting a new vehicle with maintenance support. The right choice depends on the allowance offered, business mileage reimbursement, and the employee’s personal tax position.

In many cases, electric company cars remain highly competitive versus a cash allowance because the BIK percentage is so low. By contrast, a high-emission car with a large P11D value can create a personal tax bill that makes the allowance route more appealing.

When to verify your result with official sources

This page provides an estimate, not formal tax advice. You should verify any important decision with current HMRC guidance and your employer’s payroll documentation. Official resources can change, and there may be details that affect your exact case, such as payroll timing, contributions, or vehicle classification.

Useful official sources include the UK government guide to tax on company cars, the HMRC company car benefit percentage tables, and the IRS fringe benefit guide for wider background on how non-cash benefits are treated in another major tax system.

Bottom line

A BIK tax calculator is one of the fastest ways to assess the real personal cost of a company car. The most important inputs are the P11D list price, emissions, electric range where relevant, tax year, and your income tax band. If your employer covers private fuel, always model that separately, because it can materially change the result. For many employees, especially higher-rate taxpayers, an EV can still produce a notably lower tax bill than an equivalent petrol or diesel company car.

This calculator is designed for informational use and gives an estimate based on standard UK company car BIK rules. Always confirm final figures with HMRC guidance, your payroll team, or a qualified tax adviser.