If you need to declare benefit in kind on your Self Assessment and you’re staring at the form wondering where it goes — you’re not alone. A Reddit user on r/HMRC was told by HMRC to correct their return to declare a benefit in kind, had their P11D in hand, and still couldn’t find the right section. “I’ve never had to do this before so any help much appreciated!”
The response from the community was clear: P11D benefits go in the “Employment benefits and expenses” section — a separate part of the return from where you enter your salary. The OP had been looking in the wrong section entirely.
Here’s the plain-English explanation of what benefit in kind is, what a P11D is, how the tax is calculated, and exactly where to put the numbers on your tax return.
What Is a Benefit in Kind?
A benefit in kind (BIK) is a non-cash perk you receive from your employer that has a monetary value and is taxable. According to HMRC’s guidance on benefits in kind, common examples include:
- Private medical insurance — your employer pays the premium, you pay tax on the value. If your employer pays £1,200/year for your Bupa cover, the cash equivalent on your P11D will be £1,200, and at a 40% tax rate you’ll owe £480 in tax on it.
- Company car — taxed based on CO2 emissions and the car’s list price. A £30,000 car with a 25% BIK rate generates a cash equivalent of £7,500/year. At 40% tax, that’s £3,000 in additional tax — every year you have the car.
- Interest-free or low-interest loans — taxed on the interest you saved. If your employer lends you £10,000 at 0% interest and the official rate is 2.25%, the cash equivalent is £225/year.
- Asset provided for personal use — e.g., a laptop you also use privately. Taxed on the value of the benefit, typically 20% of the asset’s market value per year.
- Accommodation — if your employer provides housing, it’s taxed on the annual value of the property (or the cost to the employer if higher).
- Fuel for private travel — in a company car, this is a separate taxable benefit on top of the car itself, with a fixed cash equivalent depending on the car’s CO2 emissions and fuel type.
The key principle: if your employer gives you something that has a value and you use it privately, it’s probably a taxable benefit. The HMRC expenses and benefits A-to-Z covers the full list.
What Is a P11D Form?
A P11D is the form your employer gives you that lists all the benefits in kind you received during the tax year. For each benefit, it shows the “cash equivalent” — the taxable value HMRC uses to calculate how much tax you owe.
Your employer also sends a copy to HMRC, so they already know what benefits you received. If you don’t declare them on your Self Assessment, HMRC will likely contact you — as happened to the Reddit user who prompted this post.
You should receive your P11D by 6 July after the end of the tax year, as required by HMRC’s P11D guidance. If you haven’t got it by mid-July, ask your employer’s HR or payroll team.
How “Cash Equivalent” Is Calculated
The cash equivalent isn’t always the same as what your employer paid. Here’s how it’s worked out for common benefits:
Company cars
The cash equivalent for a company car is calculated as:
Car’s list price × BIK percentage rate (based on CO2 emissions)
For example:
- Car list price: £28,000
- CO2 emissions: 110g/km → BIK rate: 25% (2024-25 rates)
- Cash equivalent: £28,000 × 25% = £7,000/year
- Tax at 40%: £2,800/year
- Tax at 20%: £1,400/year
The BIK percentage rate increases for higher-emission cars and decreases for electric or low-emission vehicles. A fully electric car has a BIK rate of just 2% in 2024-25, making it far cheaper in tax terms — a £30,000 electric car would have a cash equivalent of just £600/year, costing £240/year in tax at 40%.
Private medical insurance
The cash equivalent is simply the premium your employer pays. If they pay £1,200/year for your cover, the cash equivalent is £1,200.
- Tax at 40%: £480/year
- Tax at 20%: £240/year
Low-interest loans
The cash equivalent is the difference between the official interest rate and the rate you’re paying. For a £10,000 loan at 0% when the official rate is 2.25%:
- Cash equivalent: £10,000 × 2.25% = £225/year
- Tax at 40%: £90/year
- Tax at 20%: £45/year
How to Declare Benefit in Kind on Your Self Assessment
This is the part that trips people up — because the section you need isn’t where you’d expect it.
Step 1: Find the right section
Log into your HMRC Online account and open your Self Assessment return. Navigate to the “Employment benefits and expenses” section — this is separate from the main employment income section where you enter your salary and PAYE details.
If you’re amending a return, the section is in the same place — one Reddit user reported “was looking at a different section of the amended form” and missing it entirely. The section is labelled clearly once you find it, but it’s not adjacent to the employment income section, which is where most people look first.
Step 2: Enter the cash equivalent values
For each benefit listed on your P11D, enter the cash equivalent amount in the corresponding box. The form has specific boxes for common benefits:
- Box 1: Company cars
- Box 2: Car fuel
- Box 3: Private medical insurance
- Box 4: Loans
- Boxes 5–13: Other specific benefits (vouchers, assets, relocation, etc.)
- Box 14: Other benefits not covered above (entered individually with descriptions)
Don’t enter the amount your employer paid — enter the cash equivalent figure from your P11D. As shown above, these can be very different numbers.
Step 3: Submit (or resubmit if amending)
Once you’ve entered all benefits, submit your return. HMRC will calculate the additional tax you owe based on your tax bracket. The tax is collected through your Self Assessment — it’s not deducted from your salary via PAYE (though HMRC may adjust your tax code to collect it if you’re not in Self Assessment).
What If You Forget to Declare a Benefit in Kind?
If you’ve already submitted your return and realise you missed a benefit, don’t panic. You have 12 months after the filing deadline to amend, as outlined in HMRC’s corrections guidance. Log back in, add the benefit in the “Employment benefits and expenses” section, and resubmit.
If HMRC contacts you first (as happened to the Reddit user), they’re usually just asking you to correct it — no penalty for an honest mistake corrected voluntarily. See our guide on what to do if you made a mistake on your Self Assessment for the full amendment process.
Are All Benefits in Kind Taxable?
No. Some benefits are exempt from tax, according to HMRC’s tax-free benefits guidance. Exempt benefits include:
- Workplace parking — no tax due
- Business travel and subsistence (when travelling for work) — no tax due
- Trivial benefits under £50 (e.g., a birthday cake, a small gift) — no tax due, but must not be cash or a cash voucher
- Mobile phones (one per employee, if provided by employer) — no tax due
- Cycle to work schemes (under certain conditions) — no tax due on the loan of the bicycle
- Workplace nurseries — no tax due on childcare provided on-site
Your P11D should only list taxable benefits — if something is exempt, it won’t appear on the form, and you don’t need to declare it.
Can You Reduce Benefit in Kind Tax?
There are legitimate ways to reduce your BIK tax bill:
Salary sacrifice
Some employers offer salary sacrifice arrangements where you give up part of your salary in exchange for a benefit. This can reduce your overall tax bill because both you and your employer save on National Insurance. Common salary sacrifice benefits include pensions, cycle-to-work schemes, and electric cars (which have very low BIK rates).
Choose an electric company car
As noted above, electric cars have a BIK rate of just 2% in 2024-25, compared to 25%+ for petrol/diesel cars. A £30,000 electric car costs £240/year in tax at 40%, versus £3,000+/year for a comparable petrol car. The savings can be thousands of pounds per year.
Pay for private fuel yourself
If your employer provides free fuel for private travel in a company car, the taxable benefit can be significant — often £3,000–£5,000/year depending on the car. If your private mileage is low, it may be cheaper to pay for your own fuel and avoid the benefit.
Who Pays the National Insurance on Benefits in Kind?
Your employer pays Class 1A National Insurance on most benefits in kind — currently at 13.8% of the cash equivalent. This is separate from your personal tax bill and doesn’t appear on your Self Assessment. It’s an employer cost, not an employee cost.
For example, if your private medical insurance has a cash equivalent of £1,200, your employer pays £1,200 × 13.8% = £165.60 in Class 1A NIC on top of the premium.
The Bottom Line
Declaring benefit in kind on your Self Assessment is straightforward once you know where to look:
- Get your P11D from your employer (by 6 July)
- Open the “Employment benefits and expenses” section
- Enter the cash equivalent values from your P11D — not what your employer paid
- Submit
If you missed it, amend within 12 months — no penalty for honest corrections.
Calculate Your Benefit in Kind Tax
Use our P11D tax calculator below — or open it as a standalone page — to work out exactly how much tax you’ll pay on your company car, private medical insurance, or low-interest loan.
For help with other Self Assessment terminology, see our full HMRC jargon buster. If you need to correct your return, see how to amend your Self Assessment and what to do if you made a mistake.