Company Car Tax 2017/18 Calculator
Estimate the Benefit-in-Kind (BIK) value and the personal tax you might pay on a company car during the 2017/18 tax year.
Visual Overview
A quick comparison of BIK value versus personal tax cost.
Company Car Tax 2017/18 Calculator: A Deep-Dive Guide to BIK Rules, Rates, and Real-World Planning
Understanding how the company car tax works in the 2017/18 tax year can feel complex, especially if you are balancing personal tax liabilities with the benefits of a company-provided vehicle. This guide is designed to make the rules tangible and practical. It breaks down the Benefit-in-Kind (BIK) system, explains why emissions matter, and helps you compare fuel types and list prices. The calculator above provides a fast estimate, but the deeper context will help you refine your decisions and plan with confidence.
What is Benefit-in-Kind and why does it matter?
Benefit-in-Kind is a taxable value assigned to benefits you receive from your employer, such as a company car used for personal journeys. The basic logic is that if a company provides you with a valuable asset for private use, the tax system treats that asset as a form of income. In 2017/18, the BIK value for company cars is calculated using a percentage linked to CO₂ emissions, which is then applied to the car’s list price.
The BIK value is not the amount you pay in tax; instead, it is the taxable value added to your income. Your personal tax rate is then applied to the BIK value to determine your annual tax cost. This means two employees driving identical cars can pay different amounts depending on whether they are basic rate or higher rate taxpayers.
Key variables the 2017/18 calculator uses
- List price: The manufacturer’s list price including VAT and delivery, not necessarily the discounted price you negotiate with a dealer.
- CO₂ emissions: Measured in grams per kilometre. Lower emissions reduce the BIK percentage.
- Fuel type: Diesel vehicles are subject to a 4% supplement in 2017/18 (subject to a maximum BIK rate of 37%).
- Personal tax rate: Usually 20%, 40%, or 45% depending on your income band.
Why the 2017/18 tax year is significant
In 2017/18, the government tightened emissions-based thresholds to encourage cleaner company fleets. This was the period when ultra-low emission vehicles gained a substantial tax advantage, and the diesel supplement continued to influence decision-making. If you are reviewing historical company car policies, or comparing how your tax cost changed year-on-year, understanding the 2017/18 framework is essential.
| CO₂ Emissions Band (g/km) | Indicative Petrol BIK % (2017/18) | Diesel Adjustment |
|---|---|---|
| 0 | 7% (ultra-low emission) | +4% (capped) |
| 1–50 | 13% | +4% (capped) |
| 51–75 | 16% | +4% (capped) |
| 76–94 | 19% | +4% (capped) |
| 95–99 | 20% | +4% (capped) |
The table above illustrates the general shape of the 2017/18 BIK schedule. Beyond 95–99 g/km, the percentage typically increased by 1% for every 5 g/km. The maximum BIK percentage was 37%. Diesel vehicles always had a 4% supplement in 2017/18, unless that would push the vehicle beyond the 37% cap.
How the calculator estimates your 2017/18 tax cost
To estimate your personal tax cost for the 2017/18 tax year, the calculator performs a three-step process:
- Step 1: Determine the BIK percentage based on CO₂ emissions and fuel type.
- Step 2: Calculate the BIK value by applying the percentage to the list price.
- Step 3: Apply your tax rate to the BIK value to estimate your annual tax cost.
For example, if your car’s list price is £30,000, emissions are 110 g/km, and the BIK percentage is 22%, the BIK value would be £6,600. At a 20% tax rate, the estimated annual tax cost would be £1,320. That is typically spread monthly via PAYE, so you might see around £110 per month. These numbers are illustrative and can be refined by the exact BIK schedule, but the pattern remains consistent.
Diesel versus petrol: the 2017/18 policy signal
In 2017/18, diesel cars were still widely used for fleet purposes, but they attracted a BIK supplement. The extra 4% BIK reflected environmental and air-quality concerns. This increment can materially increase personal tax for drivers, and it also affects overall fleet budgets. If you are comparing similar vehicles in the same emissions band, the diesel model will almost always produce a higher tax burden in 2017/18 unless it is a qualifying low-emission or RDE2-compliant model (the latter evolved in later years).
Ultra-low emission vehicles and early incentives
By 2017/18, the tax system already provided meaningful incentives for ultra-low emission vehicles, including electric and some plug-in hybrids. Vehicles emitting 0 g/km were taxed at a lower BIK percentage than comparable petrol or diesel cars. This created a strong financial argument for employers and employees to consider cleaner vehicles, even if the upfront list price was higher. When you combine the BIK savings with lower running costs, total ownership can become more competitive than it first appears.
Why list price matters more than you think
The list price is the anchor point for BIK calculations. It includes optional extras and delivery, regardless of the discount you negotiated. That means two employees paying different purchase prices for the same model still face identical tax costs. For fleet managers and employees, this places emphasis on selecting models with the best emissions-to-list-price ratio rather than the best negotiated price. In practical terms, a high-list-price vehicle with strong emissions may still generate a higher BIK value than a moderately priced car with slightly higher emissions.
| Scenario | List Price | BIK % (Petrol) | BIK Value | Tax Cost (20%) |
|---|---|---|---|---|
| Compact hatchback | £20,000 | 19% | £3,800 | £760 |
| Executive saloon | £40,000 | 22% | £8,800 | £1,760 |
| Electric vehicle | £35,000 | 7% | £2,450 | £490 |
Interpreting your results: what the calculator is telling you
When you input values into the 2017/18 company car tax calculator, it provides two primary outputs: the estimated BIK percentage and the annual personal tax cost. Use these results as a planning tool. For example, if you are offered a car allowance instead of a company car, you can compare the cost of privately leasing a vehicle versus the tax cost of accepting the company-provided option. If you are a fleet manager, the calculator helps you predict the tax burden across different employee tax bands.
Strategic planning for 2017/18 policies
Even though 2017/18 is a historic tax year, it is still relevant for evaluating the cost of a company car at that time. Companies often revisit past tax years for auditing, policy analysis, or retroactive planning. Understanding the rules also highlights how policy evolved, and can help forecast the impact of later adjustments. When reviewing historical fleet data, consider emissions improvements over time, shifts from diesel to petrol or electric, and any changes in employee tax distribution.
Common misconceptions about company car tax
- “The discounted price reduces my tax.” Not in 2017/18. The list price is used, regardless of discounts.
- “Only high-emission cars pay BIK.” All company cars used privately are taxed, but the percentage varies by emissions.
- “The BIK value is the tax.” The BIK value is the taxable amount. Your tax rate determines your final cost.
- “Diesel is always cheaper.” The 4% diesel supplement often makes diesel more expensive in tax terms for 2017/18.
Practical tips for using a company car tax calculator
When using a calculator, always enter the manufacturer list price rather than the negotiated price. Confirm the vehicle’s exact CO₂ value from the manufacturer’s documentation, and ensure that any options are included in the list price. If you are uncertain about the fuel type category, verify whether the vehicle qualifies as a plug-in hybrid or electric. Accurate inputs make the output more reliable.
Authoritative sources and further reading
For official guidance on company car tax rules, refer to the UK government and academic resources. The following sources are helpful for understanding the statutory framework and emissions measurement standards:
- HMRC guidance on company car BIK
- Rates and thresholds for employers 2017/18
- University research on emissions and policy impacts
Final thoughts: making the most of your 2017/18 company car decision
The 2017/18 company car tax environment rewarded low emissions and penalized higher-emission and diesel vehicles. By understanding the BIK percentage thresholds and applying them to the list price, you can accurately estimate personal tax costs. The calculator above offers a fast, transparent view of how list price, emissions, and tax rate interact, while this guide provides the deeper context that can help you compare options and inform policy. Whether you are reviewing past fleet decisions or benchmarking historical cost structures, a clear understanding of the 2017/18 company car tax system remains valuable.