Most locum pharmacists invoice as sole traders, and most have done so for years without question. That history does not make the position safe. HMRC has a page in its Employment Status Manual that deals specifically with locum pharmacists, ESM4270, and its position is more cautious than the generic contractor default. Status is decided on the facts of each engagement, and those facts do not always support self-employment.
This article explains what ESM4270 says, how the three status tests apply to a pharmacist's actual working pattern, what changes if you work through your own company, and how to use CEST. It is not generic locum-contractor content: everything here is anchored on pharmacy-specific facts. For the operating structure question (sole trader vs limited company vs umbrella), see the companion post on locum pharmacist limited company vs umbrella. To model take-home under different arrangements, use the locum take-home comparator (a scenario tool, not a status determination).
The short answer: it depends on the facts, and HMRC is restrictive on locum pharmacists specifically
Self-employment is not a category you choose by deciding to invoice. It is a legal status that depends on how the engagement actually works: who controls the work, whether you can send someone else, and whether you carry real financial risk. For locum pharmacists, HMRC's ESM4270 makes the point directly. The manual addresses the pharmacist profession by name and notes that arrangements which look like flexible self-employment on the surface can have the characteristics of employment in substance.
The honest answer to "am I self-employed?" is: possibly, but the facts need to support it, and for many locum pharmacists on rota-based bookings, they do not as clearly as assumed. The sections below show why.
HMRC's locum-pharmacist page, ESM4270, and what it says
ESM4270 sits within HMRC's Employment Status Manual, which caseworkers use when investigating status disputes. Its existence matters for a specific reason: it names the pharmacist profession. Generic contractor guidance in the manual does not do that. When HMRC has taken the time to write profession-specific guidance, it is because the profession presents patterns that generic guidance does not adequately address.
The page focuses on the working arrangements typical of a booked locum shift: the pharmacy sets the date, the hours and the duties; the pharmacist works alongside or in place of the regular superintendent; the booking is typically made through an agency or a rota managed by the pharmacy group. In those circumstances, ESM4270 asks whether the pharmacist is genuinely in business on their own account or is simply filling a gap in the pharmacy's workforce under arrangements that look more like employment than freelance work.
The key takeaway from ESM4270 is not that locum pharmacists are automatically employed. It is that the self-employed status is not automatic either, and that HMRC will look at the substance of the arrangement rather than the label on the invoice.
"Everyone does it self-employed" is not a defence
The locum pharmacist market has operated on a self-employed invoicing norm for a long time. Large agency networks, NHS locum booking platforms and pharmacy groups all process locum invoices as self-employed contractor fees. That market practice does not change the legal test.
ESM4270 exists precisely because HMRC is aware of this market convention and does not accept it as determinative. If an investigation is opened and the facts of a specific engagement point toward employment, the locum (or, in IR35 cases, the fee-payer) can face unpaid income tax, Class 1 National Insurance contributions, interest and penalties for prior years. The fact that a neighbouring locum has filed the same way for ten years is not a defence. Status is assessed engagement by engagement, on the facts.
This is not a theoretical risk. HMRC has historically targeted professional sectors where self-employed working is the market norm but the substance of the arrangements does not support it. The NHS locum space is a known area of attention.
The status tests applied to a locum pharmacist: control, substitution and financial risk
The three primary tests used to decide whether someone is self-employed or employed are control, substitution and financial risk. Each needs to be applied to a pharmacist's real working pattern, not the generic contractor version.
| Test | Points toward self-employment | Points toward employment | The pharmacist reality |
|---|---|---|---|
| Control | You set your own hours, methods and workflow without direction from the client | The client dictates when, where and how you work; you are managed day-to-day | Shift times, dispensary procedures, SOPs and who you work alongside are all set by the pharmacy. GPhC clinical autonomy over individual dispensing decisions is professional regulation, not the same as commercial control over the engagement terms. |
| Substitution | You can send someone else to do the work in your place without the client's approval | The client has hired you personally; you cannot be replaced without their agreement | A substitute must be GPhC-registered, must hold the right to practise as a pharmacist, and in most cases the pharmacy and its superintendent pharmacist will need to approve the replacement. In practice, most locum bookings are personal and last-minute substitution within a shift is rarely operationally possible. The right of substitution exists in theory but is heavily constrained by professional registration requirements. |
| Financial risk | You quote for work, can profit or lose on a job, have your own equipment and client base, bear the cost of defective work | You are paid a rate for time worked; if the work goes wrong the client bears the commercial cost | Locum pharmacists are typically paid a day rate for hours attended. They do not quote to deliver an outcome and bear the shortfall if it costs more than quoted. Professional indemnity insurance is carried but relates to professional negligence, not commercial financial risk on the engagement. A fixed day rate for time is a hallmark of employment, not genuine contractor risk. |
No single test is conclusive. Status is decided by looking at all three (and other secondary factors such as exclusivity, the provision of equipment and whether the working relationship is mutually obligatory). The difficulty for many locum pharmacists is that all three tests point in the same direction: rota-set shifts, GPhC-gated substitution that rarely happens in practice, and a day rate with no downside risk.
If you work across many pharmacies simultaneously, manage your own bookings, set your own rates and actively turn down work, your position is stronger. If you cover the same pharmacy most weeks, work within its rota and have never actually sent a substitute, the position is weaker.
If you work through your own company: IR35 and off-payroll working
A significant number of locum pharmacists operate through a personal service company (a limited company of which they are the sole or majority director and shareholder). Working through a company does not resolve the status question: it adds a second layer.
IR35 (off-payroll working rules) apply where a locum's company has a contract with a pharmacy (or agency), and the underlying engagement, if it were a direct contract between the locum personally and the pharmacy, would be one of employment. When IR35 applies, the income from that engagement is treated as deemed employment income and is subject to income tax and Class 1 NIC, broadly as if the locum were on the pharmacy's payroll.
Who has responsibility for determining IR35 status depends on the size of the end client:
- Large and medium pharmacies and pharmacy groups are responsible for making a Status Determination Statement (SDS) for each engagement and, if the engagement is inside IR35, for deducting tax and NIC before paying the locum's company.
- Small pharmacy businesses (below the Companies Act size thresholds) pass the responsibility to the fee-payer in the supply chain (typically the agency), or to the locum's own company.
The IR35 status question is separate from, but uses the same tests as, the underlying self-employment question. A locum working through their own company therefore needs to satisfy both: are the engagements genuinely outside employment on the facts, and does the IR35 framework confirm that? For a detailed comparison of operating structures, see the locum pharmacist limited company vs umbrella post, and visit the locum pharmacists hub for the broader picture. The take-home comparator can model the net income difference between operating structures, though it cannot determine status.
Checking your status: CEST and its limits
CEST (Check Employment Status for Tax) is HMRC's online status-checking tool. It is the official tool of record and HMRC has committed to standing behind a result produced from accurate inputs. For that reason, running CEST for each engagement and keeping a record of the result and the inputs is a sensible step regardless of the conclusion it reaches.
CEST has a known limitation that is particularly relevant to pharmacists. The substitution question asks whether you have an unconditional right to send a substitute, and whether you have actually done so. For a pharmacist, substitution is conditional: the substitute must be GPhC-registered and, in practice, the pharmacy must be satisfied with the replacement. CEST does not know about GPhC registration requirements, so the tool frequently returns an "undetermined" result when substitution is conditional rather than unfettered.
"Undetermined" is not a safe harbour. It means CEST cannot reach a conclusion from the answers given, and HMRC may reach its own conclusion if the arrangement is investigated. An undetermined result is a signal to review the engagement terms, not confirmation that the current approach is acceptable.
CEST should be run per engagement, using accurate answers to the actual working arrangements, not the arrangements as you wish they were. Answers should be saved. If the tool returns "employed" or "undetermined" for a material proportion of your engagements, that is the point at which taking advice on the position is worth considering.
What getting it wrong costs, and what to do next
If HMRC successfully argues that an engagement was one of employment, the consequences run to prior years. The window for a standard assessment is four years from the end of the relevant tax year, extended to six years for careless errors and twenty years where there is deliberate concealment.
The financial exposure on a misclassified locum engagement typically includes:
- Income tax on earnings that were not reported on self-assessment (or reported as self-employed profit rather than employment income, with different allowable deductions)
- Employee and employer Class 1 National Insurance contributions (the self-employed Class 4 and Class 2 rates that were paid are lower than Class 1)
- Interest on unpaid amounts from the original due date
- Penalties, which can be reduced through voluntary disclosure but not eliminated
Across several years of locum work at a typical day rate, these amounts are not small. The practical steps that reduce risk are: run CEST for each engagement and document the answers, review the actual working arrangements against the three tests rather than assuming the market norm is safe, and if a material proportion of income comes from arrangements that look employed on the facts, take advice before HMRC raises the question.
The locum pharmacists hub covers the full range of tax and accounting considerations for locum pharmacists in more depth. The locum take-home comparator lets you model net income under different operating structures. It is a scenario and estimate tool that states its simplifications and is not a substitute for status advice on your specific engagements.
This article covers England. The NHS locum booking landscape in Scotland, Wales and Northern Ireland involves different regulatory frameworks; the tax and status tests are UK-wide but the NHS contract context differs. This content is general guidance, not personal advice on any specific engagement.