Your P11D contains the figures HMRC uses to tax your company benefits. When those figures are wrong, you pay the wrong amount of tax—sometimes for years without realising.
Employers make mistakes, systems miscommunicate, and employees rarely check the details.
The result is thousands of people overpaying tax on benefits they do not have, benefits valued incorrectly, or benefits that should be exempt entirely.
This guide explains how to check your P11D for common errors, what to do when you find mistakes, and how correcting your records can result in tax refunds for previous years.
Key Takeaways:
Your P11D should arrive by 6 July each year showing benefits from the previous tax year
• Company car figures are the most common source of P11D errors due to complex calculations
• Benefits you stopped receiving mid-year should show reduced values, not full-year amounts
• Some benefits are exempt from tax and should not appear on your P11D at all
• Errors on your P11D directly affect your tax code, causing ongoing over or underpayment
• You can challenge incorrect P11D figures through your employer or directly with HMRC
What Your P11D Actually Shows
The P11D is a form your employer submits to HMRC listing the taxable benefits and expenses you received during the tax year.
You should receive a copy showing what was reported on your behalf. HMRC then uses this information to adjust your tax code, increasing or decreasing the tax deducted from your salary.
The form covers benefits in kind—things of value your employer provides that are not part of your cash salary.
Common examples include company cars, private medical insurance, gym memberships, beneficial loans, and living accommodation.
Each benefit has a cash equivalent value that gets added to your taxable income.
Your employer must submit P11D information to HMRC by 6 July following the end of the tax year. For the 2025/26 tax year (ending 5 April 2026), the deadline is 6 July 2026.
You should receive your copy around the same time, though some employers provide it earlier.
If you do not receive a P11D but know you have taxable benefits, contact your payroll department.
Some employers now use payrolling for benefits, which means the tax is calculated and deducted through your regular pay rather than reported separately on a P11D.
In this case, you would not receive a P11D because the benefit value already appears on your payslips.
Why P11D Errors Happen
Mistakes occur for various reasons, and understanding the common causes helps you know what to check.
Company car calculations involve multiple variables: list price, accessories, CO2 emissions, fuel type, dates available, capital contributions, and private fuel provision.
Each element affects the taxable value, and errors in any component produce wrong figures.
A car registered with incorrect CO2 emissions could be taxed at entirely the wrong benefit in kind rate (BIK rate).
Benefits that start or end mid-year should be pro-rated. If you received a company car from September, you should only be taxed on seven months of benefit, not twelve.
If you returned the car in January, you should not be taxed on the full year. Systems do not always capture these dates correctly.
Pooled or exempt benefits sometimes appear when they should not. A pool car used by multiple employees and not available for private use is not a taxable benefit.
Workplace parking is exempt. One mobile phone per employee is exempt. If these appear on your P11D with a value, something has gone wrong.
Changes to benefits during the year create complexity. Swapping one company car for another, upgrading or downgrading health cover, or changes to loan arrangements all require accurate recording.
The final P11D should reflect the actual benefit received throughout the year, not just the position at year end.
Data entry errors can happen. Transposed digits, wrong employee numbers, benefits attributed to the wrong person, or simple typing mistakes all find their way onto P11D forms.
The more manual the process, the higher the potential error rate.
How to Check Your Company Car Figures
Company cars generate the most P11D queries because the calculations are complex and the tax amounts are significant.
A basic rate taxpayer with a car showing incorrect figures could be overpaying hundreds of pounds annually.
Start with the P11D value—this should be the car’s list price when new, including VAT, accessories, and delivery charges, minus the first year’s registration fee and vehicle tax.
Compare this to documentation from when you received the car. If you made a capital contribution toward the cost (a one-off payment, not monthly contributions), this should reduce the P11D value by up to £5,000.
Check the CO2 emissions figure and fuel type. These determine the benefit in kind percentage applied to your car.
An error here multiplies through the entire calculation. You can verify your car’s official CO2 figure through the vehicle registration document (V5C) or DVLA records.
Confirm the dates the car was available to you. The benefit should be calculated from the date you could first use it for private journeys to the date you returned it.
Periods when the car was genuinely unavailable for 30 consecutive days or more should reduce the taxable amount.
If your employer provided fuel for private use, check whether this is recorded and whether you actually received it.
The fuel benefit adds significantly to your tax bill. Some employees pay for their own private fuel and should have no fuel benefit recorded.
Others received free fuel for part of the year before arrangements changed.
Compare the figures to HMRC’s company car and car fuel benefit calculator, available on gov.uk. Input your car’s details and see what the benefit should be.
If there is a meaningful difference from your P11D, you have found an error worth investigating.
Checking Other Common Benefits
Private medical insurance values should match what your employer actually pays for your cover. If you have family cover, the full premium is typically taxable to you.
If your cover level changed during the year, the figure should reflect this.
Beneficial loans—where your employer lends you money at below-market interest rates—are taxable on the difference between what you pay and HMRC’s official rate.
Check that any loan balance is correct and that any interest you paid has been accounted for. Loans under £10,000 at any point in the year may be exempt entirely under the de minimis rule.
Relocation expenses exceeding £8,000 become taxable. If you relocated for work, check whether the amount shown reflects only the excess above this threshold.
Qualifying relocation costs up to £8,000 should not appear on your P11D.
Living accommodation provided by your employer follows specific rules. Some accommodation is exempt if it is necessary for your job, provides better performance of duties, or is customary for your type of work.
If you believe your accommodation should be exempt but it appears on your P11D, this needs investigating.
Assets made available for private use—laptops, phones beyond the first one, furniture, equipment—are taxable on 20% of the market value annually or the actual cost of provision if higher.
Check that values seem reasonable and that genuinely work-only equipment has not been included.
Benefits That Should Not Appear at All
Certain benefits are exempt from tax and should not appear on your P11D. Their presence indicates an error.
- Workplace parking provided at or near your place of work is exempt regardless of value. This includes spaces your employer owns, leases, or pays for.
- One mobile phone per employee, including line rental and private calls, is exempt provided the contract is between your employer and the phone provider.
- Personal contracts reimbursed by your employer do not qualify.
- Employer pension contributions within annual allowance limits are exempt and should not appear. The pension itself is not a P11D benefit.
- Workplace canteen meals available to all staff are exempt. Subsidised food in a staff restaurant is not taxable if all employees can access it on the same terms.
- Eye tests and corrective glasses for VDU users, where required for work, are exempt.
- Trivial benefits worth £50 or less that are not cash, not contractual, and not performance-related are exempt. A birthday gift from your employer worth £30 should not appear.
- Long service awards of up to £50 per year of service, for employees with at least 20 years’ service, are exempt if given as tangible items rather than cash.
If any of these appear on your P11D, raise the issue with your employer. They should amend their records and inform HMRC.
What Happens When Your P11D Is Wrong
Errors on your P11D flow through to your tax code. HMRC receives the P11D data, adds the benefit values to your expected income, and adjusts your code to collect the additional tax through your salary.
If your P11D overstates benefits, your tax code will be too low. You will have too much tax deducted from each pay packet.
This continues until the error is corrected—potentially for years if the same wrong figures are submitted annually.
If your P11D understates benefits, your tax code will be too high. You will underpay tax and eventually receive a bill or have future tax codes adjusted to recover the shortfall.
The P11D also feeds into your annual tax calculation. If you complete a Self Assessment return, you must report benefits in the employment section.
Using wrong figures creates inaccuracies that may trigger HMRC enquiries or cause you to pay incorrect amounts.
For employees who do not complete Self Assessment, HMRC reconciles your position through the P800 process after each tax year.
If benefits were over coded, you may receive a refund automatically—but only if HMRC spots the discrepancy.
Many errors persist because the P11D and tax code match each other, even though both are wrong.
How to Correct P11D Errors
The correction route depends on when you discover the error and your relationship with the employer.
For current or recent employers, start with payroll or HR. Explain what you believe is wrong and provide evidence.
They should investigate and, if you are correct, submit an amended P11D to HMRC. You should receive a corrected copy.
HMRC will then adjust your tax code and, if you overpaid, arrange a refund.
If your employer disagrees or refuses to amend, you can contact HMRC directly. Explain that you believe your P11D contains errors and provide details.
HMRC can investigate with your employer and make corrections to your tax record if satisfied the original figures were wrong.
For former employers, contact them in writing if possible. They retain an obligation to maintain accurate records and should correct genuine errors even after you have left.
If the employer no longer exists or will not engage, contact HMRC with whatever evidence you have.
For errors spanning multiple years, each tax year may need separate correction. However, you can address all years in a single communication with your employer or HMRC.
The four-year time limit for tax refund claims means older errors may not be fully recoverable, so act promptly when you discover problems.
Gather evidence before making contact: payslips showing benefit deductions, correspondence about benefits starting or ending, car documentation, insurance certificates, or anything else supporting your position.
The more specific you can be about what is wrong and why, the faster resolution typically comes.
Payrolled Benefits: A Different System
Some employers now payroll their benefits, meaning the taxable value is calculated and taxed through your regular pay each month rather than reported annually on a P11D.
With payrolled benefits, you will not receive a P11D for those items. Instead, the benefit value appears on your payslips, and tax is deducted as if it were additional salary.
Your tax code should not include adjustments for payrolled benefits because the tax is already being collected.
The advantage is more accurate, real-time taxation. If your benefit changes mid-year, your payslip adjusts immediately rather than waiting for year-end reconciliation.
However, errors can still occur. Check your payslips to verify the benefit values being taxed match what you actually receive.
The same types of errors—wrong car figures, incorrect dates, exempt benefits being taxed—can happen in payrolled systems just as in P11D reporting.
If you have a mix of payrolled and non-payrolled benefits, you may receive a P11D for some items but not others.
Ensure you understand which benefits fall into which category to avoid confusion about what should appear where.
Checking Your Tax Code Against Your P11D
Your tax code should reflect your P11D benefits. Understanding how to verify this helps you spot problems before they cost you money.
A standard tax code of 1257L means HMRC expects you to have no taxable benefits reducing your allowance.
If you have a company car or other P11D benefits, your code should typically be lower—perhaps 1057L, 857L, or similar depending on benefit values.
To check, take the standard personal allowance of £12,570 as an example and subtract the cash equivalent values from your P11D.
Divide by ten, and you have the number that should appear in your tax code.
If your P11D shows benefits totalling £3,000, your code should be around 957L (12,570 minus 3,000 equals 9,570, divided by ten equals 957).
Discrepancies suggest either your P11D is wrong, HMRC has not processed your P11D correctly, or there are other factors affecting your code.
Your personal tax account on gov.uk shows how HMRC calculated your tax code, letting you see which benefits they have included and at what values.
If your tax code does not match your P11D, contact HMRC for clarification. There may be a timing issue—codes at the start of the tax year are based on the previous P11D, updated when new P11D data arrives.
Or there may be a genuine error needing correction.
Reporting P11D Benefits on Your Self Assessment
If you complete a Self Assessment tax return, you must include your P11D benefits in the employment section—even though HMRC already has the figures from your employer.
Failing to report these benefits correctly is a common mistake that can trigger penalties, interest charges, or unexpected tax bills.
The employment pages of your tax return include specific boxes for company cars, fuel benefit, medical insurance, and other P11D items.
- You should transfer the figures from your P11D directly into these boxes. The cash equivalent values on your P11D are the amounts to enter, not the tax you paid on them.
- Do not assume HMRC will automatically use your P11D figures if you leave the employment section blank or incomplete.
Self Assessment is a declaration of your total income, and you are responsible for ensuring accuracy.
HMRC cross-checks your return against P11D data, and discrepancies may prompt an enquiry or correction.
If you received benefits from multiple employers during the tax year, you need separate employment entries for each.
Each employer’s P11D covers only the benefits they provided. Missing one employer’s benefits from your return understates your income and could result in underpaid tax.
Timing matters when completing your return. P11D forms for the tax year ending 5 April should arrive by early July, well before the Self Assessment deadline of 31 January the following year.
If your P11D has not arrived by the time you want to file, contact your employer rather than guessing the figures. Estimated entries that prove incorrect create complications later.
If you know your P11D contains errors but your employer has not yet corrected them, you face a choice.
You can enter the P11D figures as shown and then seek a correction once the amended P11D is issued.
Alternatively, you can enter what you believe are the correct figures and include a note in the additional information section explaining the discrepancy.
The second approach is technically more accurate but may require supporting evidence if HMRC queries the difference.
Keep your P11D with your tax return records.
HMRC can enquire into a return for up to twelve months after filing (or longer in some circumstances), and having the P11D to hand helps you respond quickly to any questions about your employment benefits.
Getting Refunds for Previous Years
If you discover your P11D has been wrong in previous years, you may be able to reclaim overpaid tax. The general time limit is four years from the end of the tax year in question.
For the 2020/21 tax year, the deadline to claim was 5 April 2025. For 2021/22, the deadline is 5 April 2026, and so on. Earlier years fall outside the time limit for most purposes.
Start by establishing what the correct figures should have been for each tax year. Then calculate the tax you should have paid versus what you actually paid. The difference is your potential refund.
Contact HMRC explaining that your P11D contained errors and you overpaid tax as a result. Provide the corrected figures and any evidence supporting your position.
HMRC will review and, if they agree, issue a refund or adjust your tax code to credit the overpayment against current tax.
For significant amounts spanning multiple years, consider seeking professional advice.
An accountant or tax adviser can help ensure you claim everything you are entitled to and present the case effectively to HMRC.
Preventing Future Errors
Taking an active role in checking your benefits reduces the chance of errors persisting.
- When you receive a new benefit, note the details: start date, value, and terms. Keep documentation—the car order form, insurance certificate, loan agreement, or whatever applies.
This gives you reference points for checking future P11D entries.
- When benefits change or end, inform payroll in writing and keep a copy. Clear communication reduces the chance of benefits being recorded incorrectly.
Follow up to confirm the change has been processed.
- Check your P11D promptly when it arrives each July. Do not file it away unopened. Compare every entry against your records and query anything that looks wrong.
It is far easier to correct current-year errors than to unravel multiple years of problems later.
- Review your tax code when it changes. HMRC issues new codes when your circumstances change or at the start of each tax year.
Each time, verify the code makes sense given your current benefits. Your personal tax account shows the calculation behind your code.
- If you complete Self Assessment, use your P11D figures carefully. Transcribing wrong P11D amounts onto your tax return perpetuates errors.
If you know your P11D is wrong, use the correct figures on your return and consider adding a note explaining the discrepancy.
P11D FAQs
Q1: When should I receive my P11D from my employer?
A: Your employer must provide your P11D copy by 6 July following the end of the tax year. For the 2026/27 tax year ending 5 April 2027, you should receive it by 6 July 2027. If you have taxable benefits but receive no P11D, check whether your employer uses payrolling instead, which means benefits are taxed through your regular pay.
Q2: What should I do if my P11D company car figures are wrong?
A: Contact your payroll or HR department with evidence of the correct figures—such as the car’s actual list price, CO2 emissions from the V5C document, and dates you had the vehicle. They should submit an amended P11D to HMRC. If they refuse, contact HMRC directly to report the discrepancy.
Q3: Can I claim a tax refund if my P11D has been wrong for several years?
A: Yes, you can reclaim overpaid tax for errors in the previous four tax years. Contact HMRC with details of the incorrect figures, what they should have been, and supporting evidence. HMRC will review your case and refund any overpaid tax.
Q4: Why does my tax code not match my P11D benefits?
A: Your tax code at the start of the tax year is based on the previous year’s P11D, then updated when new P11D data arrives. There may be a timing delay, or HMRC may have included estimated figures. Check your personal tax account on gov.uk to see how your code was calculated.
Q5: What benefits should not appear on my P11D?
A: Exempt benefits include workplace parking, one mobile phone per employee, employer pension contributions, workplace canteen meals, eye tests for VDU users, and trivial benefits under £50. If these appear on your P11D, raise the issue with your employer as an error has occurred.
