Every morning before dawn in the London docks of the early 1900s, hundreds of men gathered at the gates and waited to be chosen. A foreman would point into the crowd — you, you, not you — and the lucky ones earned a day’s pay for a day’s work. Everyone else went home with nothing. The system was called the “call-on,” and it ran on a brutal logic: a man was worth only the hours he could sell that morning.
More than a century later, thousands of doctors run their lives on exactly the same logic. The locum shift is the modern call-on. You are healthy, available, and willing, so you sell another block of hours at a good rate. But here is the catch. However high that rate climbs, you are still standing at the dock gate, earning nothing the moment you stop showing up.
I did this for years. What’s more, as a former FCA-regulated financial adviser, I really should have known better. So this post is about why the extra shift feels like progress but almost never delivers freedom — and what actually does.
The Locum Reflex
When a doctor wants more money, the locum shift is the path of least resistance. The skill is already there. The rate is already set. No product needs building, no audience needs finding, and the cash lands within weeks. Compared with the messy, uncertain work of creating something new, picking up a shift is beautifully simple.
That simplicity is exactly why it’s a trap. Because it’s so easy to reach for, most doctors never reach for anything else. The locum shift scratches the itch just enough to keep you from asking a harder question: what would it take to earn money without selling another hour of your life?
Here’s the thing, though. The extra shift isn’t wrong. Early on, trading time for a higher rate is often the fastest way to free up cash for investing. The problem starts when locuming becomes the whole strategy rather than the first rung on a ladder. Then the tool that was meant to buy your freedom quietly becomes the thing that postpones it.
The Locum Ceiling
Every time-for-money arrangement has a hard ceiling, and locuming is no exception. You can raise your rate, but you cannot add hours to the day. Consequently there is a mathematical limit to how far a shift-based income can take you, and it arrives faster than most doctors expect.
Tax makes that ceiling lower still. In 2025/26, earnings above £50,270 are taxed at 40%, so a chunk of every locum shift already disappears before it reaches your account. Push higher and it gets worse. Between £100,000 and £125,140, the personal allowance tapers away, which creates an effective marginal rate of around 60%. In other words, a consultant picking up weekend locums to cross into six figures can hand back six pounds of every extra ten to HMRC. That’s not a reward for exhaustion. That’s a penalty for it.
Then there is the cost you cannot see on the payslip. Every locum hour is an hour not spent with your family, not spent resting, and not spent building anything that might one day pay you while you sleep. Because the shift pays immediately, it feels productive. Meanwhile the compounding asset you didn’t build stays worth exactly nothing. Economists call this opportunity cost, and for doctors it is the most expensive line item of all.
Finally, the locum ceiling is guarded by burnout. The strategy that depends on you being fit enough to keep showing up collapses the moment you’re not. Illness, parental leave, or simple exhaustion can switch the income off entirely. Ultimately, an income that vanishes when you stop is not freedom. It is a well-paid dependency.
Sellable Hours vs Ownable Assets
This is the distinction that changed how I think about money, and it is worth naming clearly. There are only two kinds of income a doctor can earn. The first is the sellable hour — you exchange your time for money, once, and the transaction ends when the shift does. The second is the ownable asset — something you build or buy once that keeps paying you long after the work is done.
A locum shift is a sellable hour in its purest form. So, in truth, is a substantive NHS contract. Both are honourable, and both stop the day you do. An ownable asset behaves in the opposite way. A rental property collects rent whether you worked that month or not. A globally diversified index fund grows while you sleep. An online course, a book, or a membership keeps selling after it’s made. Each of these decouples your income from your calendar, which is the whole game.
The uncomfortable truth is that most doctors own almost no assets of either type. They own a phenomenal sellable hour and very little else. As a result, their entire financial life rests on their continued willingness to show up — which is precisely the thing burnout takes away. Shift the balance, even slightly, and everything changes. The goal isn’t to stop selling hours tomorrow. Rather, it’s to route some of the proceeds into things you can own.
The Ownership Escape
So what do you actually build? For most doctors, the escape runs along three routes, and you don’t have to pick just one.
The first is the passive-investing baseline. Before anything clever, max your tax shelters. You can put £20,000 a year into a Stocks and Shares ISA and £60,000 (including employer contributions) into pension annual allowance, and both grow free of the tax that’s mauling your locum income. This is the least glamorous route and the most reliable, because it turns surplus cash into an asset without needing a single new skill.
The second is property, which is how I built my own first real asset. Property is not passive in the way the gurus pretend, yet a well-chosen rental converts a deposit into an income stream that no longer depends on your rota. For a higher-rate taxpayer the structure matters enormously — a limited company can shelter far more than personal ownership — so this is one to model carefully before you leap.
The third route is the one doctors most underrate: productising your expertise. You already hold knowledge that people will pay for — exam coaching, teaching, writing, consulting, a niche course. Better still, HMRC gives you a £1,000 trading allowance to test an idea before any tax applies. Build it once and it can sell a hundred times. That is the exact opposite of the call-on, and it’s the lever I now pull hardest.
None of these replaces your salary overnight, and none is meant to. Instead, each one moves a little of your income out of the sellable-hour column and into the ownable-asset column. Do that consistently and one day you look up to find the next shift is optional. That’s the whole point.
Where to start this week
- Count your assets honestly. List everything you own that would still pay you if you stopped working tomorrow. If the list is short, you’ve found your real problem — and it isn’t your income.
- Redirect one shift a month. Take the after-tax proceeds of a single locum shift and route it straight into an ISA or pension rather than your current account. You’ve now converted a sellable hour into an ownable asset.
- Model the 60% trap. If your earnings sit near £100,000, work out whether the next locum shift is really worth 40 pence in the pound — pension contributions can claw the allowance back.
- Pick one asset to build. Property, index investing, or a product from your expertise. Choose the one you’d actually enjoy, because you’ll stick with it.
- Use the £1,000 trading allowance. Test a non-clinical income idea this month while it’s still tax-free. The goal isn’t a business plan. It’s proof that a pound can reach you without a shift attached.
The dockworkers of old London never escaped the call-on, because the system gave them no way to own anything. You are not so trapped. You simply have to decide that the sellable hour is your starting capital, not your ceiling.
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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.
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