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The Most Common Accounting and Tax Mistakes Dentists Make
Poor record-keeping, missed deadlines, mixed finances, wrong employment status – the 11 accounting and tax mistakes that cost UK dental practices the most.
NJ
By Neha Jain15 min read
Updated July 2026
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Most of the expensive accounting and tax mistakes made by dentists are not the result of cutting corners or taking deliberate risks. They come from not knowing what the rules require, using advice that is too generic to account for how dental practice finances actually work, or simply being too focused on clinical work to pay sufficient attention to the business side.
What this article covers
The eleven accounting and tax mistakes that come up most frequently in UK dental practices.
What causes each mistake, what it actually costs, and what fixes it.
Real observations from Samera’s specialist dental accountants on what they find most often.
Key Takeaways
Structure underpins almost everything else, tax, business and bookkeeping structure all compound if wrong from the start.
Poor record-keeping is the root cause of most other problems here, and the easiest one to fix.
Missing an HMRC deadline triggers an automatic penalty. Being late is enough, no error required.
Payments on account catch most self-employed dentists off guard the first time. Setting aside money monthly from day one avoids it.
Mixing personal and business finances is the most avoidable compliance problem. One account, one card, fixes it.
Not separating NHS and private income breaks VAT treatment and NHS pension reporting at once.
Getting associate employment status wrong now carries real backdated PAYE and NI risk since HMRC withdrew the self-employment concession in 2023.
The one mistake that underlies almost everything else
Natasha Gnanapragasam, Director of Operations, Accountancy and Tax at Samera, when asked to name the single most common mistake she sees across dental practice accounts:
“Structure. That is everything, it is the most significant thing I could think of. It can be your tax structure, your business structure, or even how you structure your accounting books and bookkeeping. Everything matters. If you don’t have a proper structure in place before you take on anything, it ends up costing you more in fees, more in taxes, more in time. Structure underpins everything else.”
Natasha Gnanapragasam Director of Operations
1. Poor record-keeping
The root cause of most other accounting problems. Receipts get lost. Transactions end up in the wrong category or are forgotten entirely. Cash purchases of clinical consumables disappear from the records entirely. By year-end, the accountant is reconstructing rather than reviewing.
The consequences are significant. Expense claims cannot be supported if HMRC opens an enquiry. Your accountant spends more time and charges more. Tax returns contain avoidable errors. And nobody in the practice has had a reliable view of how it is actually performing for months.
The fix is not complicated: keep digital records of everything, reconcile your bank account monthly, and review the financial picture regularly. Cloud accounting software has made this substantially less time-consuming than it used to be.
Reconciling accounts monthly and keeping digital records from day one is exactly what our ongoing accountancy service handles, so this stops being something you have to manage yourself.
Missed HMRC deadlines trigger automatic penalties. You do not need to have made an error. Simply being late is enough. The most commonly missed in dental practices:
Self Assessment: 31 January. An automatic £100 penalty applies from the moment the deadline passes.
Corporation Tax: nine months and one day after the accounting year-end.
VAT returns: one month and seven days after each quarterly period.
RTI submissions: on or before every single payday. Not monthly. Every pay date.
P60s: 31 May. P11Ds: 6 July.
A rolling deadline calendar combined with accounting and payroll software that handles electronic submissions automatically solves most of this. For a full compliance guide, see our article on compliance and Making Tax Digital.
This is the most common financial shock in dental self-employment and it is almost always caused by nobody explaining it in advance. Payments on account are advance payments towards the following year’s tax bill: half due in January alongside the current year’s bill, half in July. In a high-earning year you could effectively be paying two years’ worth of tax simultaneously in January.
The fix is simple and completely reliable: set aside a percentage of income monthly into a dedicated tax savings account from the very first month of self-employment. Your accountant can suggest a realistic percentage.
Charles Suthakran, Business Development Executive, Accountancy and Tax at Samera, on why this is consistently the most avoidable compliance problem he sees:
“One business account, one business card, used for nothing else. It sounds almost too basic to be worth saying, but it’s the single thing that causes the most trouble. What happens is that one account ends up doing two jobs, the practice’s and the owner’s. It reconciles fine day to day, so nobody worries. The problem only shows up when HMRC asks a question, because you have to prove a cost was a business cost, and you can’t do that cleanly if it’s tangled up with personal spending. A legitimate claim you’re fully entitled to gets disallowed simply because you can’t evidence it.”
Charles Suthakran Dental Accountant
5. Under-claiming allowable expenses
Many dentists pay more tax than they need to because they assume certain expenses do not qualify without ever checking. Natasha on what is most consistently missed:
“The most common things missed are use of home, associates don’t understand how to claim it, so we educate them, and travel between practices. But beyond those, they also don’t understand the entertainment allowance for each employee per year, or that they can claim for loupes and clinical equipment they’ve bought. These are small things but they all add up. Proper guidance makes all the difference.”
Use of home, travel between practices, the entertainment allowance, clinical equipment like loupes, these are the exact areas our associate accounts service is built to catch.
6. Not separating NHS and private income in the accounts
This one is specific to dentistry and it comes up in almost every set of mixed practice accounts Samera reviews. NHS and private income get recorded together, usually because the bookkeeping software has not been set up to separate them, and the downstream consequences are significant.
The first problem is VAT. Most NHS clinical income is exempt. Some private cosmetic work is taxable. Product sales are taxable. If income streams are bundled together, the correct VAT treatment cannot be calculated and partial exemption cannot be applied accurately.
The second problem is NHS pension calculations. Associates and practices both have reporting obligations to the NHSBSA based on NHS pensionable earnings. If NHS income is not tracked separately, those calculations are unreliable. Errors in NHS pension reporting typically surface only when someone is approaching retirement.
The third problem is management information. If you cannot see how much of your income is NHS and how much is private, you cannot make informed decisions about treatment mix, pricing, or whether an associate arrangement is actually profitable.
Natasha on why this genuinely requires specialist knowledge:
“Dentists need to know how to recognise the income, NHS and private, and how to record it. Because beyond every set of numbers, there are special nuances that apply. Those nuances can only really be determined by a specialist accountant. Not by a general accountant. That’s one of the most important distinctions between what a specialist does and what a generalist does in this space.”
Getting the NHS and private split right from the start protects your VAT position, your NHS pension reporting, and your ability to actually see how the practice is performing.
7. Getting the VAT position wrong on cosmetic work and retail
Most clinical treatment is VAT-exempt but purely cosmetic procedures and product sales are generally taxable. Getting this wrong creates under-declarations that HMRC can pursue going back several years. For practices with mixed income, partial exemption rules limit how much input VAT can be reclaimed. Specialist VAT review is worth the cost for any practice generating meaningful income from cosmetic or retail work.
Treating associates as self-employed when their practical working arrangement looks like employment can result in the practice owing back PAYE and National Insurance on all payments made, plus interest and penalties, potentially going back several years. This risk increased significantly when HMRC withdrew the specific concession treating dental associates as self-employed by default in April 2023.
The test is not what the contract says. It is what the working arrangement actually looks like in practice. Use HMRC’s CEST tool for each associate independently and keep the results on file.
9. Staying in the wrong business structure too long
Most dentists start in a structure that makes sense at the time. The mistake is not reviewing it as income grows and responsibilities change. An associate earning modestly as a sole trader is in the right structure. That same person ten years later as an established practice owner with significant profits probably is not. Review your structure every two to three years.
Tax planning is only useful when done in advance. The strategies that produce the best outcomes, pension contributions, capital allowances timing, BADR qualification for a future sale, all require lead time. Dentists who plan throughout the year pay less tax than those who start planning when the bill arrives.
11. Using a generalist accountant for a specialist area
Natasha on what she finds when a practice switches from a generalist accountant to Samera, and what gets corrected first:
“When a new dental client boards with us, most of them don’t have the correct approach to bookkeeping. Either they’re on cash basis when accruals would be more accurate, or there are incorrect categorisations throughout. And the NHS income nuances, how to allocate it, how to split it from private, how it feeds into pension calculations, that’s almost always been handled incorrectly. That’s the first thing we correct. And it matters because every number beyond it is built on that foundation.”
Natasha Gnanapragasam Director of Operations
A generalist accountant will commonly miss NHS income structures, employment status risks for associates, partial VAT exemption in mixed practices, capital allowances on clinical equipment, NHS pension complexity for both employed staff and associates, and BADR qualifying conditions for practice sales. The cost of specialist advice is almost always less than the cost of the errors it prevents.
Natasha on the financial consequences she sees most often:
“The most expensive outcome I have seen is not the tax itself, it is the penalties and interest that follow when something has gone wrong and was not rectified quickly. HMRC charges very heavy interest. The penalties are significant. If something has gone wrong and there’s a payment delay, the client ends up paying penalty and interest charges on top of the tax they already owe. That combination is the most costly thing. And it is almost always avoidable with proper systems and proper advice from the start.”
Penalties and interest are the costliest part of any HMRC issue, not the original tax. Tax Investigation Insurance Cover means Samera handles the enquiry on your behalf without the bill landing on you directly.
The dentists who avoid them are not particularly financially sophisticated. They just do the straightforward things: keep tidy records, separate NHS and private income from the start, use good software, review their structure periodically, and work with people who actually understand dental practice. None of it is complicated. It just requires doing it consistently.
Dental Accounts Mistakes: FAQs
What is the single most common mistake dental practices make with their accounts?
Structure. That covers tax structure, business structure, and how the bookkeeping itself is set up. Getting any of these wrong from the start tends to compound, costing more in fees, tax, and time the longer it goes uncorrected.
What happens if personal and business finances are mixed together?
It reconciles fine day to day, so the problem often goes unnoticed until HMRC asks a question. At that point, a cost has to be proven as a business cost, and that can’t be done cleanly if it’s tangled up with personal spending. Legitimate claims can get disallowed simply because they can’t be evidenced.
What is the penalty for a late Self Assessment return?
An automatic £100 penalty applies from the moment the 31 January deadline passes, regardless of whether any tax is owed. Further daily penalties of £10 apply from three months late, plus larger fixed penalties at six and twelve months. Interest is charged on any unpaid tax from the due date.
Why does it matter whether NHS and private income are recorded separately?
Three reasons. First, VAT: the correct treatment and partial exemption calculations cannot be applied accurately if income streams are bundled. Second, NHS pension: reporting to the NHSBSA is based on NHS pensionable earnings, which cannot be accurately calculated without separate tracking. Third, management information: you cannot make good decisions about treatment mix or pricing if you cannot see the split between NHS and private.
How far back can HMRC investigate a dental practice?
For innocent errors, typically up to four years. For careless errors, up to six years. For deliberate errors or fraud, up to twenty years. Employment status errors where associates were incorrectly treated as self-employed can result in PAYE and NI assessments going back several years with interest applied throughout.
Can employment status errors be corrected after the fact?
It is possible, but expensive. HMRC will typically require payment of all unpaid PAYE and National Insurance plus interest for every affected year, and may also impose penalties. Correcting the position voluntarily before HMRC identifies it through a compliance check is considerably less costly than being discovered.
Is a specialist dental accountant worth the additional cost?
For the vast majority of dentists, particularly practice owners, anyone in a group structure, and anyone planning a future sale, yes. The cost of specialist advice is typically recovered many times over through better expense claims, correct tax planning, avoided penalties, and better-structured business arrangements over time. The NHS and private income nuances alone can only be handled correctly by a specialist.
Glossary
CEST (Check Employment Status for Tax) – HMRC’s tool for assessing whether a working arrangement should be treated as employed or self-employed for tax purposes, used to test each associate individually.
PAYE (Pay As You Earn) – HMRC’s system for collecting Income Tax and National Insurance directly from employment income as it’s paid.
RTI (Real Time Information) – The requirement to report pay and deductions to HMRC on or before every payday, rather than at year end.
Payments on account – Advance payments towards next year’s Self Assessment tax bill, due in January and July, based on the previous year’s liability.
Partial VAT exemption – The rules governing how much input VAT a practice can reclaim when it has a mix of exempt (most NHS clinical work) and taxable (cosmetic, retail) income.
NHS pensionable earnings – The portion of income that counts towards NHS Pension Scheme benefit calculations, which must be tracked separately from private income to report accurately.
Employment status – Whether a working arrangement is treated as employed or self-employed for tax purposes, based on the actual working relationship rather than what a contract states.
BADR (Business Asset Disposal Relief) – A relief that reduces the Capital Gains Tax rate on qualifying business disposals, including practice sales.
Capital allowances – Tax relief for the cost of qualifying equipment and assets, including clinical equipment such as loupes.
Neha Jain is a skilled content writer with a rich background in business and financial knowledge. With a bachelor’s degree in English Literature and Psychology, Neha has honed her writing skills, furthering her expertise with the Content Writing Master Course (CWMC) at IIM SKILLS and a Content Marketing Certification from HubSpot Academy.
Working alongside our business development experts, Neha specialises in helping accountants, dentists and other healthcare professionals start, scale and sell their businesses.
Arun, founder and CEO of Samera, is an experienced accountant and dental practice owner. He specialises in accountancy, building businesses, financial directorship, squat practices and practice management.
Natasha specialises in accounting and tax for dental and healthcare businesses, helping clients improve tax efficiency, streamline financial systems, and build scalable processes for long-term growth.
Charles specialises in bookkeeping, year-end accounts, company secretarial work and tax return preparation, helping clients maintain accurate records, smooth financial processes and compliant reporting.
Need help with your dental accounts?
Samera works with dental associates, practice owners and dental groups to manage accounts, tax, bookkeeping and financial reporting. If you want clearer numbers, less admin and a system that works throughout the year, book a free consultation with our dental accounting team.
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