Meet two doctors. Same grade, same NHS trust, same starting salary five years ago. Both decided they needed more money. Both found an extra ten hours a week they could redirect.
Dr A filled those hours with locum shifts. Reliable, predictable. Fifty weeks a year, ten hours a week, year after year.
Dr B spent those same hours differently. Started a newsletter. Built a short online course for junior doctors. Started writing on LinkedIn. Quietly, without anyone really noticing.
Five years later:
Dr. A is still working those ten hours. Same hourly rate — maybe marginally better after some negotiation. More experienced. More tired. The balance of five years of extra effort: some holidays, a dent in the mortgage, and a lower back that’s starting to ask questions.
Dr B’s newsletter has over 3,000 subscribers. The course sells each month passively. The LinkedIn audience generates consulting enquiries. Monthly passive income: roughly £2,000 and growing [VERIFY — illustrative figure]. The asset — the audience, the email list, the course — has real sellable value. And it keeps compounding while she’s on nights.
Same ten hours. Completely different trajectories.
This isn’t a story about grind culture or quitting medicine. It’s a story about compounding — and why the medical career model is specifically designed to keep doctors away from it.
The Locum Ceiling
Let’s be precise about what ten locum hours actually earn you.
An ST4+ Emergency Medicine doctor on NHS bank shifts earns roughly £40–70 per hour, depending on day, time, and trust. Call it £55/hour for this exercise. Ten hours a week, fifty weeks a year: £27,500 gross.
After income tax at 40% and National Insurance — assuming you’re already above the higher-rate threshold from your substantive role, which most senior trainees and consultants are — you’re keeping somewhere around £15,000–16,500 net per year.
That’s real money. Genuinely useful money.
But here’s the ceiling nobody talks about: in five years, you’ll still be earning the same per hour.
The locum rate doesn’t compound or multiply. Every pound requires you to physically show up — next week and every week after. The skills you’re selling are your own, not scalable. You can’t delegate the shift or sell the work as an asset.
What you have after five years of locum work is not an asset. It’s the income you successfully extracted from a fixed number of hours. The moment you stop, it stops.
Economists have a name for this: trading time for money at a linear rate. The medical profession runs almost entirely on this model. Most doctors never question whether there’s an alternative.
The Asset Comparison
Now let’s model what those same ten hours look like if redirected — not abandoned, just redirected — toward something that compounds.
Three realistic options for a UK doctor:
A newsletter. Covering a clinical topic, a career niche, or a financial theme relevant to your peers. Costs almost nothing to start. At 1,000 engaged subscribers, you have a platform. At 3,000, you have leverage. At 5,000, you have an asset with real commercial value — whether that’s a paid tier, course sales, sponsorship, or a consulting pipeline.
An online course. Built around something you already know: exam prep, a clinical skill, a procedure, a career pathway, a financial concept relevant to doctors. Built once. Sold indefinitely. Requires maintenance, not reconstruction.
A content presence on LinkedIn or Substack. Quiet in the first twelve months. Slowly compounding after that. The platform that eventually feeds everything else.
None of these produces meaningful income in year one. That’s the honest truth, and it’s also the reason most doctors never start. Year one is an investment: the returns are slow, but the foundation is being built for future growth. In year two, the results begin to build on themselves — little progress creates further opportunities. From years three to five, compounding becomes clear: new subscribers, clients, or sales multiply on top of previous ones, and growth accelerates even if you don’t increase effort. This is the power of compounding in action.
A rough comparison — all figures illustrative, for educational purposes only [VERIFY]:
| 1 | ~£15,500 | ~£500 |
| 2 | ~£15,500 | ~£3,000 |
| 3 | ~£15,500 | ~£8,000 |
| 4 | ~£15,500 | ~£14,000 |
| 5 | ~£15,500 | ~£24,000 |
By year five, the digital asset has crossed over. Thanks to compounding, the platform can keep growing and generating income even while you take a break. Unlike locum income, which resets each week, an asset keeps earning on past work — so your earlier efforts continue to deliver benefits beyond your immediate input.
More importantly, the locum route ends when you do. The asset route ends when you choose to sell it — or pass it on.
The Real Cost of Locum Time
The headline number — £55/hour, net £33 after tax — doesn’t tell the full story.
Three things erode the real value of locum income that most doctors fail to model.
The tax drag is worse than you think. If your substantive salary already takes you to £100,000, every pound of locum income above that threshold is taxed at an effective marginal rate of 60%. Why? Because you lose £1 of personal allowance for every £2 earned above £100k. That £55 locum shift earns you around £22 net [VERIFY]. Most doctors at that income level have no idea this is happening to them — and their accountant hasn’t told them either.
The NHS pension interaction. Additional locum income earned through a limited company or agency doesn’t count towards your NHS pension. You’re forgoing defined benefit accrual in one of the best occupational pension schemes in the world — and substituting it with heavily taxed income you’ll likely spend rather than invest. The compound cost of that substitution, modelled over twenty years, is significant [VERIFY — worth modelling a specific comparison].
The fatigue cost. This one doesn’t appear on any spreadsheet. Extra clinical shifts compound stress, increase cognitive strain, and quietly degrade performance in your substantive role. The evidence on physician burnout is extensive. Ten extra clinical hours a week isn’t neutral to the remaining forty. It erodes them. The locum income is partly subsidised by a cost you’re paying elsewhere — in your concentration, your energy, your lasting sustainability.
The locum hour is less valuable than it looks. The building hour is more valuable than it looks.
What the Shift Looks Like in Practice
This is not an argument for quitting locum work. That income is real, often necessary, and for many doctors, the right call right now. The argument is for parallel construction — starting construction while the locum income is still running.
Here’s what it looks like practically:
Five locum hours a week instead of ten. The net income drop is roughly £4,000–4,500 a year after tax drag. That’s a real number, and it deserves a real decision — not a casual one.
The other five hours go into building. Not five hours thinking about developing something. Five hours actually writing, creating, publishing, and distributing.
Year one is sacrifice. Year two, a side project is gaining traction. Year three, diversification. Year five, strategy.
The doctors who make this switch almost all say the same thing later: I wish I’d started sooner. Not because the early returns are impressive — they aren’t — but because compounding only works forward. Every year you delay is a year of compounding you can never recover.
There’s one more thing the locum hours never build that the asset hours always do: evidence of expertise outside the NHS. An audience. A portfolio of published work. A product with reviews and a track record. As the medical profession continues evolving — staffing models, AI integration, portfolio careers — the doctors who have built something external will have options that purely clinical doctors simply won’t. That optionality has value that goes well beyond the income number.
Three Steps You Can Take This Week
- Audit your true locum net rate. Use HMRC’s income tax calculator and factor in your full substantive salary first. If you’re earning above £100k including locum income, your actual net hourly rate will surprise you — and probably not pleasantly.
- Identify one topic you already know deeply that a junior version of you would have paid to learn faster. That topic is the seed of a newsletter, a course, or a content presence. Write the topic down. Write three subtopics underneath it. You’ve just started.
- Spend two hours this week creating rather than earning. One newsletter draft. One LinkedIn post. One course outline. It doesn’t need to be good — it needs to exist. The compounding starts the moment you publish something and continues.
For more topics on building a life of time and financial freedom, sign up for our weekly newsletter at www.building-out.com
This post is for educational purposes only and does not constitute financial advice. Always do your own research and, if needed, ask for advice from a qualified financial adviser regulated by the FCA. No matter what stage you’re at, the most powerful step is simply to begin. Every hour redirected to building your asset today puts you one step closer to the freedom and options you want tomorrow.
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