Why HMRC Letters Often Contradict Your Accountant’s Figures
- Adil Akhtar
- 20 minutes ago
- 16 min read
Understanding Why HMRC Letters and Accountant Figures Clash in UK Tax Scenarios
Imagine that you've just received a letter from HMRC claiming you owe more tax than what your accountant calculated, and suddenly your stomach drops. As a tax accountant with over 18 years advising clients across the UK, from bustling London offices to quiet home-based businesses in the Midlands, I've seen this scenario play out countless times. It's frustrating, isn't it? But don't panic – these discrepancies often stem from simple timing issues or data mismatches, especially when losses and gains are involved. In the 2025/26 tax year, with the personal allowance frozen at £12,570 and average overpayments hitting £3.47 billion across 5.6 million taxpayers in recent years, understanding why this happens can save you money and stress. Let's dive straight in.
The Core Reasons Behind HMRC and Accountant Disagreements
I admit that none of us loves tax surprises, but here's how to spot them early. HMRC letters often contradict accountant figures because of differences in data timing – your accountant might use year-end estimates, while HMRC pulls real-time info from employers or banks. For instance, capital gains or losses from investments can be reported differently; HMRC might offset losses against gains in one way, but your accountant could apply them across multiple years for better relief. In my experience, clients with side hustles see this most, as unreported gains push up liabilities unexpectedly.
How Losses and Gains Amplify These Mismatches
Be careful here, because I've seen clients trip up when handling losses. Under UK rules for 2025/26, capital losses can offset gains, but only up to the £3,000 annual exempt amount before tax kicks in at 18% for basic-rate payers or 24% higher. If your accountant factors in carried-forward losses from prior years, but HMRC's letter reflects only current data, you'll see a gap. Gains from property sales, for example, might be taxed immediately by HMRC, while your accountant plans to defer via reliefs like incorporation – a common pitfall for business owners I've advised in Manchester.
Front-Loading the Facts: Key 2025/26 Tax Rates and Stats
So, the big question on your mind might be: What's changed this year? The personal allowance remains £12,570, with basic rate tax at 20% on income up to £50,270 in England, Wales, and Northern Ireland. But watch for regional twists – Scotland's starter rate is 19% up to £15,397, escalating to 48% top rate over £125,140. Wales mirrors England. Overpayments are rife; HMRC data shows millions overpaid billions in 2023-24 due to code errors, and with frozen thresholds amid inflation, real burdens rise by about 2-3% annually for average earners.
Table: 2025/26 Income Tax Bands Across UK Regions
Region | Band | Threshold | Rate |
England/Wales/NI | Personal Allowance | Up to £12,570 | 0% |
England/Wales/NI | Basic | £12,571-£50,270 | 20% |
England/Wales/NI | Higher | £50,271-£125,140 | 40% |
England/Wales/NI | Additional | Over £125,140 | 45% |
Scotland | Starter | £12,571-£15,397 | 19% |
Scotland | Basic | £15,398-£27,491 | 20% |
Scotland | Intermediate | £27,492-£43,662 | 21% |
Scotland | Higher | £43,663-£75,000 | 42% |
Scotland | Advanced | £75,001-£125,140 | 45% |
Scotland | Top | Over £125,140 | 48% |
This table highlights how regional variations can cause HMRC letters to differ if your accountant overlooks Scottish residency, for example – something I've corrected for several clients relocating north.
Real-World Impact:
Now, let's think about your situation – if you're an employee with a side income. Take Fizz from Birmingham, a fictional but typical client based on my cases. Fizz earns £45,000 salaried, plus £5,000 from freelance gigs. His accountant calculated £6,500 tax liability, factoring in deductible expenses. But HMRC's letter showed £7,200 owed, due to unreported freelance gains and an emergency tax code applied mid-year. By verifying via his personal tax account, we spotted the mismatch and reclaimed £700.
Step-by-Step: Verifying Your Tax Code Online
Don't worry, it's simpler than it sounds. First, sign into your HMRC personal tax account – you'll need your National Insurance number and a Government Gateway ID. Check your tax code (e.g., 1257L for standard allowance); if it's BR or OT, you're likely overtaxed. Update employer details if wrong, and download your P60 for cross-checks. This process takes 10 minutes and has helped my clients avoid thousands in overpayments.
Quick Checklist for Employees Spotting Overpayments
● Review your latest payslip against HMRC's estimate.
● Confirm multiple income sources are declared.
● Calculate manual liability: Subtract £12,570 allowance, tax 20% on next £37,700.
● If overpaid, claim via form P87 or online.
In one case, a London teacher I advised used this to reclaim £1,200 after a wrong code from a job change.
Navigating Multiple Income Sources: A Common Pitfall
Honestly, I'd double-check this if you have varied taxable incomes – it's one of the most overlooked areas. Employees with rentals or gigs often see HMRC letters inflate figures because side earnings push them into higher bands without deductions applied. For 2025/26, if your total exceeds £50,270, expect 40% on excess. Your accountant might net losses from one source against gains, but HMRC processes separately until reconciled.
Rare Cases: Emergency Tax and Its Hidden Costs
Ever been hit with emergency tax? It's brutal but fixable. This happens on new jobs or pensions, taxing at 20-45% without allowance. In my practice, a retiree client faced a £2,000 overcharge in 2024 because HMRC didn't update promptly. For 2026, request a P45 transfer immediately and monitor via app – prevents contradictions in letters.
Tailored Advice for Employees in 2026
If you're PAYE-only, focus on code accuracy. With inflation eroding frozen allowances, your real tax rate effectively rises. I've had clients in similar boats save by claiming uniform allowances or home office reliefs – up to £312 annually. Start by estimating your liability: Gross pay minus allowance, times rate band.
Self-Employed and Business Owners – Why the Numbers Diverge and How to Reconcile Them
Now, let's turn to the self-employed and limited company directors – the group where I see the most dramatic clashes between HMRC letters and accountant-prepared figures. If you're running your own business, whether as a sole trader, freelancer, or through a limited company, the gap often feels personal. I've had clients in tears over unexpected tax demands that seemed to come out of nowhere. The good news? Most of these are fixable once you understand the mechanics.
The Self-Assessment Timing Trap
Let's suppose that you submit your Self Assessment tax return by 31 January 2026 for the 2024/25 tax year. Your accountant has carefully calculated your taxable profit after allowable expenses, losses carried forward, and any qualifying reliefs. HMRC sends you a payment on account letter for 2025/26 based on last year's liability – but it doesn't reflect any losses you incurred in the current year. Suddenly you owe a huge sum. This is one of the most common reasons for apparent contradictions. For 2025/26, payment on account is still based on the previous year's tax bill (unless you claim to reduce it). If your profits have dropped significantly – say due to a big bad debt or investment in equipment – you can request a reduction via your personal tax account or by calling HMRC. I've helped dozens of clients halve their January/July payments this way.
Capital Allowances vs. Actual Cash Outlay
Be careful here, because this trips up many business owners. Your accountant might show a healthy profit after claiming capital allowances (e.g., 18% writing-down allowance on plant and machinery, or 100% Annual Investment Allowance up to £1 million). But HMRC's computer systems sometimes lag in applying these properly if your return is amended or if you have multiple income sources.
Take Emily, a graphic designer from Leeds I advised in 2024. She bought £18,000 of computer equipment in 2024/25. Her accountant deducted the full amount via AIA, reducing her taxable profit to £22,000. HMRC's initial calculation (before the return was processed) showed £38,000 taxable – triggering a £3,200 higher tax demand. Once the return was fully processed, the figures aligned.
Trading Losses – Carry-Back, Carry-Forward, or Offset?
This is where things get particularly sticky. For 2025/26, if you're a sole trader or partnership, you have options for utilising trading losses:
● Carry forward against future profits of the same trade
● Offset against other income in the current year
● Carry back up to three years against previous profits (terminal loss relief allows one-year carry-back if you cease trading)
Your accountant might choose the most tax-efficient route. HMRC's first letter might assume the default (carry-forward only) and therefore show a higher liability. I've seen clients save £4,000–£12,000 simply by electing the right loss relief on their tax return.
Side Hustles and the Gig Economy – The Hidden Reconciliation Problem
Honestly, this is one of the biggest blind spots I see in 2025/26. Many people run a “proper” business and have a side gig (Etsy shop, tutoring, dog walking). HMRC now receives data from platforms under the OECD rules (from 2024 onwards). If your side income exceeds £1,000 (trading allowance), it must be declared.
Your accountant might net the side income against main business losses. HMRC might initially treat it separately, especially if the platform reports gross figures. Result: a letter saying you owe tax on the side income without loss relief. Always declare side income on the same Self Assessment as your main trade to maximise relief.
Scottish and Welsh Variations for the Self-Employed
If you live in Scotland or Wales, your income tax rates differ even if you're a sole trader. Scotland's 2025/26 bands are more compressed, so a £60,000 profit pushes you into the 42% band much earlier than England's 40%. Your accountant should apply the correct rates, but HMRC's initial calculation letters sometimes default to England/Wales rates if residency isn't clearly flagged.
A client of mine in Edinburgh was nearly £1,800 out because his accountant (based in London) used English rates. Always double-check the residency flag on your tax return.
National Insurance – Class 2 Abolition and Class 4 Changes
Big change here for 2025/26: Class 2 NI was abolished from April 2024, but you still get credits if profits exceed £6,725 (the Lower Profits Limit). Class 4 is 6% on profits between £12,570 and £50,270, then 2% above.
HMRC sometimes sends letters showing Class 2 demands for earlier years or miscalculating Class 4. Your accountant should exclude Class 2 for current years. If you see it, challenge immediately.
Reconciling Your Business Tax Figures
Here's a simple worksheet you can recreate on paper or spreadsheet. Use figures from your 2024/25 accounts and compare to HMRC's letter.
Business Reconciliation Worksheet – 2025/26 Tax Year
● Step 1: Start with your accountant’s taxable profit £ ________ (after expenses & capital allowances)
● Step 2: Add back any non-allowable expenses HMRC might disallow (e.g., entertaining, private use of car) £ ________ Adjusted profit: £ ________
● Step 3: Deduct any loss relief claimed Current year offset: £ ________ Carry-back: £ ________ Net taxable profit: £ ________
● Step 4: Apply personal allowance (if not used elsewhere) £12,570 or tapered if income > £100,000 Taxable amount: £ ________
● Step 5: Apply correct tax rates (use table from Part 1) Tax due: £ ________
● Step 6: Add Class 4 NI 6% on £12,571–£50,270 + 2% above £50,270 NI due: £ ________
● Step 7: Total liability per accountant £ ________ (tax + NI)
● Step 8: Compare to HMRC letter total £ ________ Difference: £ ________
If the difference is more than £100–£200, contact HMRC or your accountant with this breakdown.
High-Income Child Benefit Charge – The Sneaky One
If your adjusted net income exceeds £60,000, you must repay 1% of Child Benefit for every £200 over £60,000 (full clawback at £80,000). Many self-employed people forget to include pension contributions or gift aid when calculating this. Your accountant might deduct qualifying payments; HMRC’s letter might not. Always check your personal tax account for the charge.
When HMRC Is Actually Right (And Your Accountant Isn’t)
Sometimes the letter is correct. Common errors I’ve corrected for clients:
● Claiming 100% private phone bills as business expense
● Not restricting motor expenses for private use
● Forgetting to add balancing charges on sold assets
● Misclassifying capital vs revenue expenditure
If the gap is significant, ask your accountant to review specific items against HMRC’s Business Income Manual (BIM) – it’s surprisingly readable.
Next Steps for Business Owners
Once you’ve used the worksheet, you have three main options:
If you owe less than HMRC says → Submit evidence via your tax account or write to HMRC.
If you owe more → Pay promptly to avoid interest (currently 7.75%).
If you’re unsure → Book a professional review (yes, even if you already have an accountant – a second opinion can be invaluable).
Advanced Scenarios, Rare Cases & How to Stay Ahead of HMRC Discrepancies
We've covered the basics for employees and the complexities that self-employed people and business owners face. Now let's move into the more advanced – and sometimes quite rare – situations that can cause HMRC letters to wildly contradict your accountant's carefully prepared figures. These are the cases that often catch even experienced taxpayers off guard, and I've seen them lead to five-figure surprises (in both directions).
The High-Income Child Benefit Charge Trap for Business Owners
If your adjusted net income exceeds £60,000, you start repaying 1% of your Child Benefit for every £200 over the threshold – and it's fully clawed back at £80,000. Many business owners think this only applies to salary. Wrong. It includes all taxable profits, dividends, rental income, savings interest, and even certain pension contributions.
In 2025/26, the charge is calculated on your total adjusted net income before deducting pension contributions or Gift Aid donations. Your accountant might have advised you to make a large pension contribution to drop below the threshold – but if HMRC's letter is issued before that contribution is processed, it will show the full charge.
Real client example (names changed): Mark, a limited company director from Bristol, had £78,000 adjusted net income in 2024/25. His accountant recommended a £20,000 pension contribution to wipe out the charge. HMRC sent a £2,900 repayment demand in October 2025 because the pension contribution hadn't yet appeared on their system. We appealed successfully once the contribution was confirmed, but Mark had to wait six months for the refund.
Quick tip: If you're close to the £60,000 or £80,000 thresholds, always keep a copy of your pension contribution receipt and submit it to HMRC immediately if you receive a charge letter.
The Frozen Personal Allowance & the £100,000+ Taper Nightmare
The personal allowance remains frozen at £12,570 until at least 2028. But the real killer is the taper: for every £2 you earn over £100,000, you lose £1 of personal allowance. At £125,140, your allowance disappears completely – creating an effective 60% tax rate on income between £100,000 and £125,140.
Many accountants forget to apply the taper correctly when preparing draft figures. HMRC's automated systems apply it instantly. Result: your accountant shows you paying 40% tax on that slice of income; HMRC says 60%.
Example calculation (2025/26 rates – England/Wales/NI):
● Income £110,000
● Personal allowance reduced by £5,000 (£10,000 excess ÷ 2) → £7,570 allowance
● Taxable income = £110,000 – £7,570 = £102,430
● Tax due = (£50,270 – £7,570) × 20% + (£102,430 – £50,270) × 40% = £8,540 + £20,864 = £29,404
● Without taper: (£110,000 – £12,570) × 20%/40% = £26,404
● Difference: £3,000 extra tax purely because of the taper.
If your accountant hasn't shown this taper in their workings, their figures will be £2,000–£5,000 too low.
Emergency Tax Codes on New Businesses or Second Jobs
This one still surprises me after 18 years. When you start a new job or take on a second employment, HMRC often applies an emergency tax code (usually 1257L M1 or W1). This taxes you as if you're earning that amount every month – no cumulative allowance.
A client of mine, Sarah from Newcastle, started a limited company in April 2025 and paid herself a £4,000 monthly salary. HMRC applied emergency code. She was taxed at 40% on the entire amount from month one. Her accountant had planned for basic-rate tax after the allowance was spread across the year. The first payslip showed nearly £1,600 tax deducted instead of £474. It took three months and several phone calls to get it corrected – and she had to wait until the end of the tax year for the overpayment refund.
Action point: If you see M1 or W1 on your payslip, contact HMRC immediately and request a new tax code. Provide evidence of your expected annual income.
Multiple Sources of Income & the Order of Deductions
HMRC applies personal allowance and tax bands in a specific order:
Earned income (PAYE salary, self-employment profits)
Savings income
Dividend income
This can create unexpected results when you have losses or reliefs.
Example: You have £40,000 salary + £20,000 rental profit + £5,000 dividends. Your accountant might offset a £10,000 trading loss against the rental profit first. HMRC's system will apply the loss against salary first (highest tax rate). Result: different tax liability.
Always check how HMRC has allocated losses in their calculation summary.
Welsh & Scottish Rates – The Residency Flag Trap
If you move between England and Scotland (or Wales), or even spend significant time in more than one nation, HMRC needs to know your main residence for income tax purposes. Many clients forget to update their address or residency status on their tax return. HMRC defaults to England/Wales rates, but if you're Scottish resident, you could be underpaying (or overpaying if your accountant used Scottish rates incorrectly).
The 2025/26 Changes That Are Still Causing Confusion
● Class 2 NI abolished (but voluntary contributions still possible for gaps)
● Class 4 NI reduced to 6% (was 9%)
● Capital gains annual exempt amount still £3,000
● Furnished holiday lets regime abolished from April 2025 – many landlords saw unexpected tax increases
● Non-dom regime replaced with new foreign income & gains regime from 6 April 2025
If your accountant prepared figures before these changes were fully understood, or if HMRC's systems haven't yet caught up, you'll see discrepancies.
Final Reconciliation Checklist – Use This Every Year
Print this out or save it – it's the exact checklist I give my clients at year-end.
Confirm your residency – England/Wales/NI or Scotland?
Check your tax code(s) – especially if you have multiple employments
Reconcile all income sources – ensure side hustles, rentals, dividends are included
Verify loss relief allocation – did HMRC apply it the way you intended?
Check capital allowances & balancing charges – especially if you sold assets
Confirm pension contributions & Gift Aid – for high-income child benefit charge & taper relief
Apply correct regional tax rates
Calculate payment on account reduction if profits have fallen
Check for emergency tax codes on new jobs or businesses
Review HMRC calculation summary (available in your personal tax account)
Summary of Key Points
HMRC letters often contradict accountant figures due to timing differences – accountants use estimates or planned reliefs; HMRC uses real-time or default data.
Self-employed taxpayers can reduce payments on account if profits have fallen – many miss this and pay thousands unnecessarily.
Trading losses offer multiple relief options – choosing the wrong one (or none) is a common cause of inflated HMRC demands.
The high-income child benefit charge catches out many business owners because it includes all taxable income, not just salary.
The personal allowance taper creates a 60% effective tax rate between £100,000 and £125,140 – often missed in draft calculations.
Emergency tax codes on new jobs or businesses can double your tax bill temporarily – always challenge them quickly.
Regional tax variations (especially Scotland) can cause significant differences if residency isn't correctly flagged.
Side hustles and gig economy income are now reported directly to HMRC – ensure they're declared on the same return as your main trade to maximise loss relief.
Always use the reconciliation worksheet and checklist to compare your accountant's figures against HMRC's letter line by line.
If the difference is more than a few hundred pounds, don't ignore it – contact HMRC or get a second professional opinion. Most discrepancies are fixable, and acting quickly can save you interest, penalties, and months of worry.
Stay proactive, keep good records, and check your personal tax account regularly. Tax doesn't have to be a surprise – with the right checks, you can stay one step ahead of HMRC.
FAQs
Q1: What exactly does 'CIS status' refer to in the UK construction sector?
A1: Well, it's worth noting that your CIS status essentially tells you whether you're registered as a subcontractor under the Construction Industry Scheme, and if so, at what deduction rate—typically 20% for registered or 30% if not. In my experience advising builders in the Midlands, this status determines how much tax is withheld at source by contractors, acting as a prepayment towards your final bill. Think of it like a safety net for HMRC to ensure taxes are collected upfront, especially handy if you're self-employed and juggling multiple sites.
Q2: How can someone confirm if they're registered as a CIS subcontractor?
A2: In my years helping sole traders, the simplest way is logging into your HMRC personal tax account via the Government Gateway—once in, head to the CIS section to view your registration details. If you're not tech-savvy, a quick call to the helpline on 0300 200 3210 does the trick, but have your UTR ready. I've seen clients in London forget they registered years ago, leading to mix-ups with deductions, so always cross-check annually.
Q3: Is there a way to check CIS status without an online account?
A3: Absolutely, though it's a bit old-school—write to HMRC with your Unique Taxpayer Reference and National Insurance number, requesting a status confirmation. From dealing with older tradesmen in Birmingham, I know this postal route takes about 15 working days, but it's reliable if digital access is an issue. It's a common fallback for those who've misplaced login details.
Q4: What steps should a contractor take to verify a subcontractor's CIS status?
A4: As a contractor, you must verify before paying—log into the CIS online service and input their details like name, UTR, and NI number; it'll spit out their deduction rate instantly. In my practice, I've advised firms where skipping this led to penalties, like one Manchester outfit fined for assuming a subbie's status without checking.
Q5: Can limited companies have a CIS status, and how do they check it?
A5: Yes, limited companies acting as subcontractors need to register too, and checking is similar: via the business tax account online. Picture a small plumbing firm I worked with in Leeds—they accessed their status through the company gateway, confirming gross payment to avoid unnecessary deductions on invoices.
Q6: How does someone apply for gross payment status under CIS?
A6: You apply during registration or later via your online account, proving a good compliance history and turnover thresholds—over £30,000 for sole traders, scaled up for companies. In my experience with high-earning joiners, getting gross means no upfront deductions, but it requires spotless tax records; one client missed it by forgetting a late filing.
Q7: What happens if a subcontractor's CIS status is incorrectly listed as unregistered?
A7: That means 30% deductions instead of 20%, hitting cash flow hard—appeal via your account or helpline with proof of registration. I've seen this with a freelancer in Wales who relocated; HMRC hadn't updated, leading to over-deductions refunded only after a Self Assessment claim.
Q8: Are there regional differences in checking CIS status for Scotland or Wales?
A8: CIS itself is UK-wide, but Scottish or Welsh tax bands affect your final liability after deductions—check status the same way, but factor in devolved rates during Self Assessment. A Scottish bricklayer I advised noticed no difference in status checks, but his higher band meant reclaiming less than expected.
Q9: How can gig economy workers in construction verify their CIS status?
A9: If you're picking up odd jobs via apps, register as a subbie first, then check online like anyone else. It's a common mix-up for gig workers, but one client from the gig scene in Bristol found his status lapsed after irregular work, triggering higher deductions on a big project.
Q10: What if someone has multiple jobs—does that affect CIS status checks?
A10: Not directly, but ensure all contractors verify your single status; check centrally via HMRC to avoid inconsistencies. In my time with multi-job trades, like a painter with side gigs, one forgot to update details, causing mismatched deductions across employers.
About the Author:
Adil Akhtar, ACMA, CGMA, serves as CEO and Chief Accountant at Pro Tax Accountant, bringing over 18 years of expertise in tackling intricate tax issues. As a respected tax blog writer, Adil has spent more than three years delivering clear, practical advice to UK taxpayers. He also leads Advantax Accountants, combining technical expertise with a passion for simplifying complex financial concepts, establishing himself as a trusted voice in tax education.
Email: adilacma@icloud.com
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