Hygiene and therapy are profit centres in most modern practices — and the most common place we find employment-status risk quietly accumulating. Here is what the tests look at, what getting it wrong actually costs, and how to price each route honestly.
Guide · Updated July 2026
Whether a hygienist or therapist is employed or genuinely self-employed is not a label you choose. It is a conclusion the working facts either support or do not, and the contract's title page carries very little weight against what happens on a Tuesday morning. If the conclusion goes against you, the practice carries the cost: back PAYE and National Insurance, employer's National Insurance, holiday pay, pension auto-enrolment duties, plus interest and penalties. The clinician has generally paid their own income tax in the meantime, but that does not extinguish the practice's employer liabilities.
What makes this the quiet risk rather than the loud one is drift. An arrangement set up honestly in 2019 with a genuinely independent clinician becomes, four years later, a fixed diary, a practice uniform, a guaranteed day rate and appraisals — and nobody ever revisited the paperwork.
A flat day rate, a practice-controlled diary, practice equipment and no real substitution is, in substance, employment — whatever the agreement is called.
In HMRC v Professional Game Match Officials Ltd [2024] UKSC 29, decided on 16 September 2024, the Supreme Court unanimously held that the minimum requirements of mutuality of obligation and control were satisfied in relation to individual engagements, even though the referees could turn matches down and the engagements were short. The point that matters for a dental practice is this: the old comfort blanket — "she can decline a session, so there is no mutuality" — does not survive. Mutuality can exist within each accepted session on its own.
The case was then returned to the First-tier Tribunal for the final stage of the analysis, which concluded the referees were not employees. That is the second half of the lesson and the more useful one: passing the mutuality and control threshold does not decide status, it merely gets you to the question. The overall picture — substitution, financial risk, independence, how the arrangement actually operates — still decides it. What the case removed was a shortcut, not the test.
Worked example — illustrative, using 2026/27 rates. A hygienist is paid a fee share of £60,000 a year and treated as self-employed. The arrangement has run for four years, and on the facts it is employment. Leaving aside the PAYE and employee National Insurance exposure, the employer costs alone are:
That is £67,251.60 before interest, before penalties, and before any PAYE or employee National Insurance HMRC seeks from the practice. One clinician, one arrangement, four years. A practice with three hygienists and two therapists on the same basis is looking at a materially larger number.
On how far back it can reach: HMRC's normal assessing time limit is four years from the end of the tax year, extended to six years where the behaviour was careless and twenty years where it was deliberate. The four-year example above is the mild version.
Employment is not the expensive option — it is the option whose cost is visible. If you want to control the diary, integrate the clinician into the team and own the patient relationship, employ them and price the role honestly.
Worked example — illustrative. A hygienist employed on a salary of £42,000: employer's National Insurance is 15% of £37,000 = £5,550, and auto-enrolment is 3% of £35,760 = £1,072.80. Total employment cost £48,622.80 a year, with holiday already inside the salary. That is the figure that belongs in your staff-cost ratio and in any appraisal of whether the hygiene book pays — not the £42,000.
Note the auto-enrolment thresholds while you are there: the earnings trigger for automatic enrolment is £10,000, so a part-time hygienist earning above that must be enrolled, and one earning below it retains the right to opt in. Getting this right is a payroll process, not a judgement call.
Self-employment works when the facts are real. Build it so that every element points the same way:
HMRC's Check Employment Status for Tax tool is worth running and worth keeping, but treat it as evidence rather than as a ruling: it is only as good as the answers you give it, and its output is built on the same facts a tribunal would weigh. It records the position you took and why, which is useful. It does not make an arrangement compliant that the day-to-day reality contradicts.
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Yes, but only where the facts genuinely support it rather than because the contract says so. That means real control over their own diary and clinical method, pay linked to work done rather than a guaranteed flat day rate that runs regardless of the list, a substitution right that could actually operate, their own GDC registration and indemnity, and no involvement in the practice's employment processes such as appraisals or holiday approval. The working reality carries far more weight than the label on the agreement. The most common failure is not a bad initial set-up but drift: an honest arrangement that has quietly become a fixed rota over several years.
The practice bears the cost, not the clinician. On a hygienist paid £60,000 a year over four years, the employer exposure alone in 2026/27 terms is roughly £33,000 of employer's National Insurance at 15% above the £5,000 secondary threshold, £28,968 of holiday pay at 12.07%, and £5,284 of auto-enrolment pension at 3% of qualifying earnings — around £67,000 before interest, penalties, or any PAYE and employee National Insurance HMRC pursues. Multiply that across several clinicians engaged on the same basis and the figure becomes a balance-sheet event rather than an irritation.
Decide on substance rather than habit. If you want to control the diary, integrate them into the team and own the patient relationship, employ them and price the role properly: a £42,000 salary costs about £48,623 in 2026/27 once employer's National Insurance and auto-enrolment are added, and that is the figure that belongs in your staff-cost ratio. If the clinician genuinely runs their own book with real independence, self-employment can work — but build it so the pay model, the working reality and the paperwork all say the same thing, and review it annually rather than at the point HMRC asks.
A genuinely self-employed clinician is not a worker for auto-enrolment purposes, so no employer duty arises. That is precisely why the status question matters so much: if the engagement is later found to be employment, the auto-enrolment duty is found to have existed all along, alongside the National Insurance and holiday pay. For employed hygienists and therapists the rules are mechanical — the automatic enrolment earnings trigger is £10,000 a year, the employer minimum is 3% of qualifying earnings in the band between £6,240 and £50,270, and anyone earning below the trigger still has the right to opt in.
The normal assessing time limit is four years from the end of the relevant tax year. Where tax has been lost through careless behaviour that extends to six years, and where the behaviour was deliberate it extends to twenty. Most practices assume the four-year window and are right to model it as the mild case, because an arrangement that was documented as self-employment while operating visibly as employment is exactly the fact pattern that invites a careless finding. The practical consequence is that a long-standing arrangement carries far more exposure than a recent one, which is why the review is worth doing before it is asked for.
It helps, and it is worth running and keeping, but it does not settle anything on its own. CEST produces an answer from the answers you give it, so an arrangement described optimistically will return an optimistic result that the day-to-day reality would contradict. Its real value is as contemporaneous evidence: it records the position you took, the facts you took it on, and the date. Run it for every hygienist, therapist and associate arrangement, save the output with the contract, and re-run it whenever the working pattern changes — a rota change is exactly the sort of drift that moves the answer.
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