Why HMRC Looks at Associate Self-Employment

Most associate dentists in the UK treat their NHS and private work as self-employment. They file a Self Assessment tax return, pay Class 4 National Insurance, and claim practice expenses. This arrangement has been the norm for decades. But HMRC does not accept the label "self-employed" simply because the contract says so.

HMRC challenges associate self-employment when the actual working relationship looks more like employment than self-employment. The tax authority has won several tribunal cases against dental associates in recent years, and the trend is not slowing. If HMRC reclassifies you as an employee, the consequences include backdated PAYE tax, employer and employee National Insurance, interest, and penalties. The practice that engaged you may also face employer NI bills and late-filing penalties.

This article explains the three legal tests HMRC applies, the specific facts that trigger a challenge, and what you can do to protect your position. It is general guidance only. Every case turns on its own facts, so you should take specialist advice.

HMRC and employment tribunals use a common law framework to decide whether a worker is self-employed or an employee. The tests come from case law, not statute. The three most important are control, substitution, and mutuality of obligation. No single test decides the outcome. The tribunal weighs all factors together.

Control Test

Control asks: does the practice tell the associate what to do, when to do it, and how to do it? A genuinely self-employed associate controls their own clinical decisions, appointment scheduling, and working methods. An employee follows the practice's directions.

In practice, many associates have a high degree of clinical autonomy. That is expected for a registered dental professional. But HMRC looks at the non-clinical aspects. If the practice dictates your working hours, sets your patient list, requires you to attend practice meetings, or controls your holiday dates without negotiation, those are employment indicators.

A common flashpoint is the practice manager or principal telling the associate "you must work Tuesday and Thursday 9-5" without room for negotiation. If the associate cannot rearrange those sessions without permission, control is likely present.

Substitution Test

Substitution asks: can the associate send a replacement to perform the work? A genuine self-employed person can send a suitably qualified substitute without needing the practice's consent. An employee cannot.

Many associate agreements include a substitution clause, but the test is whether the clause is realistic and operable. If the contract says you can send a substitute but in practice the principal would never accept one, or the substitute must be approved by the practice, HMRC will argue the right is not genuine.

For a substitution right to be effective, the substitute must be able to perform the same clinical duties, be paid directly by the associate (not the practice), and bear their own professional risk. If the practice insists on interviewing or approving every substitute, the right is hollow.

Mutuality of Obligation

Mutuality of obligation (MOO) asks: is the practice obliged to offer work, and is the associate obliged to accept it? In a true employment relationship, the employer must provide work and the employee must do it. In a self-employment arrangement, either side can walk away without penalty.

For associates, MOO often breaks down in practice. If the practice guarantees a minimum number of UDAs per month and the associate is expected to deliver them, that looks like an obligation on both sides. If the associate can refuse sessions without consequence, MOO is weaker.

HMRC also looks at the financial risk the associate bears. A self-employed associate typically pays for lab fees, materials, indemnity, and CPD. If the practice covers all those costs, the associate bears little financial risk, which points toward employment.

What Triggers an HMRC Challenge

HMRC does not audit every associate. They target cases where the facts suggest employment. Common triggers include:

  • Fixed sessions with no flexibility. The associate works the same days every week, cannot swap sessions, and cannot refuse work.
  • Practice provides all equipment and materials. The associate does not pay for lab fees, consumables, or surgery rent.
  • Practice sets the fee split unilaterally. The associate has no ability to negotiate the percentage or the UDA rate.
  • Practice handles all patient records and bookings. The associate has no control over appointment scheduling or patient allocation.
  • Associate takes no financial risk. If the associate is paid even when patients do not attend, or if the practice guarantees a minimum income, that looks like employment.
  • Associate is treated as part of the practice team. Attending staff meetings, wearing a practice uniform, using a practice email address, and being described as "our associate" on the website all point toward employment.

HMRC also uses IR35 rules for associates who work through a limited company. Since April 2021, medium and large practices must decide the IR35 status of any associate who provides services through a personal service company (PSC). If the practice determines the engagement is inside IR35, the associate must be paid through PAYE, regardless of the contract wording.

The BDA Model Agreement Is Not a Shield

Many associates and principals believe that using the British Dental Association's model associate agreement guarantees self-employed status. This is a dangerous assumption. HMRC and tribunals look at the actual working practice, not the paperwork. If the day-to-day reality looks like employment, the contract will not protect you.

In the 2022 tribunal case HMRC v. Kieran Mullins, a dental associate had a written agreement that stated he was self-employed. The tribunal looked at the facts: the practice set his hours, provided all equipment, paid him even when patients cancelled, and he could not send a substitute. The tribunal ruled he was an employee for tax purposes. The contract wording did not save him.

The same principle applies to locum dentists. A locum working through a limited company for a single practice over many months may be inside IR35 if the practice controls the work. The locum dentist tax page on this site covers the specific IR35 risks for locums.

How to Strengthen Your Self-Employment Position

If you are an associate and want to reduce the risk of an HMRC challenge, consider these practical steps:

  • Negotiate a genuine substitution clause. Ensure the contract allows you to send a substitute without the practice's prior approval. Keep evidence that you have exercised this right, even once.
  • Bear financial risk. Pay for your own lab fees, materials, indemnity, and CPD. If the practice covers these, you look more like an employee.
  • Control your own schedule. Negotiate the ability to set your own working days and sessions. Avoid fixed, non-negotiable rotas.
  • Do not accept guaranteed income. If the practice guarantees a minimum number of UDAs or a minimum monthly payment, that weakens your self-employment case.
  • Keep your own patient list. If possible, build a private patient list that follows you if you leave the practice.
  • Do not attend practice staff meetings. Attending team meetings suggests integration into the practice, which is an employment indicator.
  • Use your own email and marketing. Avoid using the practice's email address or being listed as part of the practice team on its website.

These steps are not always possible in every practice. The reality is that many associates work in arrangements that look more like employment than self-employment. If that describes your situation, you should speak to a dental-specialist accountant to understand your risk and plan accordingly.

What Happens If HMRC Challenges You

If HMRC opens an enquiry into your self-employment status, they will ask for evidence of your working arrangements. They may request:

  • Your associate agreement
  • Records of your working hours and sessions
  • Evidence of substitution rights exercised
  • Details of who pays for lab fees, materials, and indemnity
  • Correspondence with the practice about your working terms

If HMRC concludes you are an employee, they will issue a determination requiring the practice to operate PAYE on your earnings. The practice will owe employer NI at 15% on earnings above £5,000 per year (2025/26 rate). You will owe employee NI and income tax on the reclassified earnings. Interest runs from the date the tax should have been paid. Penalties apply if HMRC considers the error careless or deliberate.

The practice may also face penalties for failing to operate PAYE. This can create tension between the associate and the principal, especially if the practice did not budget for the backdated tax bill.

Practical Steps for Practice Owners

If you are a practice principal engaging associates, you also have a stake in this issue. If HMRC reclassifies your associates as employees, you face the employer NI bill and penalties. To reduce your risk:

  • Review your associate agreements with a dental-specialist solicitor. Ensure the contract reflects the actual working relationship.
  • Do not treat associates as employees. Do not require them to attend staff meetings, wear a uniform, or follow fixed rotas.
  • Let associates bear their own costs. If you pay for their lab fees or indemnity, you are blurring the line.
  • Consider whether your associates genuinely have control over their work. If they do not, you may need to restructure the arrangement or accept that they are employees.

For more detailed guidance on structuring associate relationships, see our page for practice principals.

Final Thoughts

HMRC's focus on associate self-employment is not going away. The tax authority has made it a priority area, and tribunal decisions continue to go against associates whose working arrangements look like employment. The key takeaway is this: your contract matters, but your day-to-day reality matters more.

If you are an associate dentist and you are unsure whether your arrangement would survive an HMRC challenge, take advice now. Waiting until HMRC opens an enquiry is far more expensive and stressful. A dental-specialist accountant can review your working practices, identify risks, and help you restructure if needed.

Our team at Dental Finance Partners works exclusively with UK dentists. We understand the specific tax issues that affect associates, principals, and locums. If you would like to discuss your situation, contact us for a confidential conversation.