By Dr. Ndubuisi “Andy” Egwim – MBBS, former NHS Salaried GP, author of The Moneywise Doctor.
Moneywise Doctor provides financial education, not regulated financial advice.
Picking up extra shifts seems like a simple way to boost income. Then the tax on that extra income comes in higher than expected. HMRC taxes overtime and extra shifts at your marginal rate, not your average rate. This means the tax on additional income can run significantly higher than the tax on your regular salary, especially near a threshold. Your payslip shows one rate on your regular pay. But an extra shift can carry a different rate, depending on where it lands.
This guide explains why this happens. It also covers what to check before you assume extra shifts always mean a proportional rise in take-home pay.
Why this matters for doctors specifically
Doctors often pick up extra shifts, locum work, or additional sessions on top of a substantive role. This pattern makes marginal tax rates especially relevant. Extra income regularly stacks on top of an already-substantial base salary. A doctor near £50,270 who takes an extra shift may find that shift taxed at a noticeably higher rate than their usual pay. A doctor near £100,000 faces an even sharper effect, since that’s where the personal allowance taper begins.
Before you commit to a pattern of extra shifts, it helps to know where your income sits relative to these thresholds. The Tax Hack X-Ray Scorecard can help you check this in under two minutes.
What actually happens to tax on extra income
UK Income Tax works in bands, not as a single flat rate on your whole salary. Each band taxes only the portion of income within it, at that band’s rate. This means:
- The basic rate band taxes income at 20%.
- The higher rate band taxes income at 40%.
- The personal allowance taper zone removes tax-free allowance as income rises, which creates a higher effective rate on that portion.
Extra shifts add to your total income for the year. Depending on where your regular salary sits, that additional income can land in a higher band. Your average pay alone won’t tell you which band.
The key rules to understand
- Your marginal rate applies to your next pound of income, not your whole salary. Near a threshold, the rate on an extra shift reflects where that specific pound falls. It doesn’t reflect your average rate for the year.
- Thresholds don’t reset per employer or per shift. HMRC counts your total income across the tax year. Locum income, substantive salary, and any other earnings all combine toward the same thresholds.
- Your tax code and payroll system don’t always catch this in real time. PAYE can sometimes apply an emergency or default rate to extra shifts at first. HMRC usually corrects this later, but the gap can cause confusion about what you actually owe.
Common mistakes doctors make around this
- They assume every extra shift carries the same rate as their regular salary. They don’t check where their total income sits for the year.
- They don’t realise that extra income near £100,000 can trigger the personal allowance taper. That portion of income then carries a heavier effective rate than expected.
- They plan spending around gross extra earnings, rather than the amount likely to reach their account after tax.
- They don’t track combined income from multiple sources, substantive role, locum shifts, and other work. Many only see the full picture when a Self Assessment bill or tax code adjustment arrives.
What to check before taking on extra shifts
Check roughly where your total income sits against the £50,270 and £100,000 thresholds before you commit to extra shifts. Consider whether the extra income might push part of your earnings into a higher band or into the taper zone. Either shift changes the real value of that income after tax. Review your payslips periodically to confirm your tax code and deductions reflect your actual combined income.
When to get professional advice on this
Extra shifts and locum work on top of a substantive role add up fast, especially near £50,270 or £100,000. A regulated adviser or accountant can help you understand the real after-tax value of additional work. They can also flag whether any planning is worth considering for your specific situation.
Frequently asked questions
Are extra shifts taxed at a higher rate than my normal salary?
Not automatically, but they can be. It depends on where your total income sits for the year. Extra income that pushes part of your earnings into a higher band carries the higher rate on that portion.
Why does an extra shift near £100,000 get taxed so heavily?
Income between £100,000 and £125,140 triggers the personal allowance taper. This creates a higher effective rate on that portion, on top of the standard higher rate.
Does it matter which employer pays for the extra shift?
No. HMRC counts your total income across the tax year, not income per employer. All sources combine toward the same thresholds.
Will my tax code automatically account for extra shifts?
Not always immediately. PAYE can apply an initial default rate to extra income before correcting it. Check your payslips and tax code to catch this early.
Should I turn down extra shifts because of the tax?
Not necessarily. Extra shifts can still raise your take-home pay overall. Understanding the real after-tax value helps you decide whether the extra work suits your specific situation.
Related reading
- How the Personal Allowance Taper Actually Works (Beyond the 60% Trap)
- Salaried GP vs GP Partner: Which Pays More After Tax?
- How Much Tax Do NHS Doctors Pay in 2026? A Full Breakdown by Grade
- Can NHS Doctors Retire at 55, 57, or 60? The Financial Implications
Find out where your income sits before your next extra shift
Extra shifts don’t always add up the way you’d expect after tax. The Tax Hack X-Ray Scorecard is a two-minute diagnostic built for doctors that checks your income, allowances, and reliefs against the thresholds that matter most.
It helps you:
- See where your income sits relative to key tax thresholds
- Understand the real after-tax value of extra work
- Get a clear next step, whether that’s a simple fix or a conversation with an adviser