How much should a locum GP set aside for tax?

It depends on your profit, because the rates are banded — there is no single correct percentage. On the worked example above, £88,200 of fees in England with no other income, the answer is 29.2% of gross fees, being £22,712 of income tax and £3,021 of Class 4 National Insurance. Set aside more than you think you need in year one: the first bill arrives with a payment on account attached.

Why is my first 31 January tax bill so much bigger than expected?

Because you pay one and a half years of tax at once. The balancing payment for the year just ended is due, and the first payment on account towards the current year is due on the same day. On the example above that turns £25,733 into £38,599. The second payment on account follows that July.

Do payments on account apply to me?

They apply if your income tax plus Class 4 National Insurance for the year exceeds £1,000. Student loan repayments are excluded from the test and from the instalments themselves. Where they apply, each instalment is 50% of that combined figure.

How is a locum GP's NHS pension contribution tier decided?

90% of your gross fee is pensionable. That pensionable pay is then annualised — scaled up over your days of pensionable service to what a full year would have been — and the tier is read off the annualised figure, not off what you actually earned. In the example above, £79,380 of pensionable pay across 248 days annualises to £116,829, which lands in the 12.5% tier. Starting part way through a year, or working irregular sessions, can therefore cost you a higher tier on the same money.

Does paying into the NHS pension reduce my tax bill?

It reduces your income tax at your marginal rate, capped at the income tax actually due. It does not reduce Class 4 National Insurance, because a pension contribution is not a trading expense, and it does not reduce the student loan repayment. The contribution is also cash leaving your account, so your total outgoings rise even though your tax falls — which is why this calculator shows the tax set-aside and total money out as two separate percentages.

Does it work if I pay Scottish income tax?

Yes for the tax. Scottish rates and bands, including the advanced and top rates, are applied to the income tax calculation. The NHS pension side uses the England, Wales and Northern Ireland contribution tiers, so if you are in the SPPA scheme treat the pension contribution as indicative and check the SPPA tiers.

First-year self-employed doctor · 2026/27

GP Locum Tax Calculator

Turn first-year tax panic into a plan — a personalised set-aside number, a dated money timeline and a setup checklist, built for UK GPs in their first 12 months of self-employment.

Projections and figures are based on what you enter. Not financial advice — speak to a regulated adviser before making decisions.

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Your first year, in a few numbers

Takes about 5 minutes. Your answers are worked out on your device — we only send something if you ask us to email your PDF.

Date you first went self-employed

Where are you taxed?

Wales and Northern Ireland use the same income-tax bands as England.

Sessions per week (typical)

Typical session rate

Expected annual profit

Pre-filled from 6 × £350 × 42 billable weeks ≈ £88,200. Adjust it to your best guess — you can change it any time.

Expected annual expenses (optional)

Blank is fine — we then treat your gross fees as equal to profit, which gives a slightly higher, safer set-aside.

Any other employed (PAYE) income this tax year?

e.g. a salaried GP post or hospital work. A rough figure is fine — it just sets which tax band your locum profit stacks into.

Pensioning your locum work?

Already registered for self employment with HMRC?

Built for sole-trader locum and salaried GPs. Limited company modelling is out of scope for now.

What this calculator does

It works out what to hold back from your locum fees in your first year of self-employment, and when the money actually has to leave your account. You give it your sessions and rate, whether you are pensioning the work, and where you pay tax; it returns a set-aside percentage, a dated timeline through to the filing deadline, and a setup checklist.

The first year is the one that catches people out, because the tax on it is not due until the January sixteen months after you start — and when it does arrive it arrives with a payment on account attached. Free, and every figure is worked out in your browser.

How the numbers are worked out

The liability. Income tax on your profit, plus Class 4 National Insurance, plus any student loan repayment through Self Assessment. Scottish rates and bands are applied if you pay Scottish income tax, and the personal allowance taper between £100,000 and £125,140 is handled properly — so the 60% effective band shows up where it should.
Two percentages, kept apart. The headline set-aside is tax as a share of your gross invoiced fees, before pension. The second figure is total money out, after pension tax relief and the contribution itself. Adding pension moves these in opposite directions, so merging them into one number would mislead you whichever way it landed.
Expenses are optional. Leave them blank and gross fees are treated as equal to profit, which deliberately overstates the set-aside percentage rather than understating it. The tool’s own expenses and rates reference has the mileage and home-working figures.
Payments on account. If your income tax plus Class 4 exceeds £1,000, HMRC asks for two instalments of 50% towards the following year. The first falls on the same day as your first bill, which is what makes that January so expensive.
Pension contributions are annualised. 90% of your gross fee is pensionable. The tier you pay is then set by that pensionable pay scaled up to a full year over your days of service — not by what you actually earned. Start late in the year and the tier is set as though you had earned at that rate all year.
Pension relief is applied narrowly. Contributions reduce income tax at your marginal rate, capped at the income tax actually due. They do not reduce Class 4 National Insurance, which is not a trading expense, and they do not reduce the student loan charge.

A worked example

6 sessions a week at £350, over 42 billable weeks, is £88,200 of fees. Starting in the August of the tax year, pensioning the work, no other income, England. These are the calculator’s own figures:

Income tax of £22,712 and Class 4 National Insurance of £3,021 — £25,733, or 29.2% of gross fees to set aside for tax.
The first bill is not £25,733 but £38,599: that year’s tax plus a first payment on account of £12,866 towards the next. 50% more than the year actually cost, on one day.
Here is the trap. Pensionable pay is £79,380, but with only 248 days of service it annualises to £116,829 — which sets the contribution tier at 12.5%, the top one. The contribution is £9,923 on pay of £79,380.
Which is why there are two percentages. Tax alone is 29.2% of gross. After £3,969 of tax relief, and the contribution itself leaving the account, total money out is 35.9% — 6.7% more, not less.

The annualisation point is worth reading properly if you work part-year or irregular sessions, because it is the difference between two pension tiers on identical earnings: the locum GP pension guide covers it, and the session rate calculator works the same figures backwards from the take-home you want.

What it doesn't cover

Estimates from the figures you enter, on 2026/27 rates. Not tax advice, and it files nothing on your behalf. Also:

Scottish pension tiers. Scottish income tax is supported, but the pension figures use the England, Wales and Northern Ireland tiers. If you are in the SPPA scheme, the tax is right and the contribution is not.
Making Tax Digital. The timeline assumes a genuine first year with no qualifying prior return, so quarterly reporting does not apply yet. If you have filed before, check where you stand.
One trade, one year. No VAT, no limited company, no partnership profit-share, no capital allowances beyond the expenses you enter, and no carrying losses between years.
The annual allowance. A pension contribution this large can bring the annual allowance into play, which is a separate calculation — see the annual allowance calculator.
Salaried work. Built for self-employed locum fees. If you are a salaried GP, the Type 2 form guide is the place to start.

Frequently asked questions

How much should a locum GP set aside for tax?: It depends on your profit, because the rates are banded — there is no single correct percentage. On the worked example above, £88,200 of fees in England with no other income, the answer is 29.2% of gross fees, being £22,712 of income tax and £3,021 of Class 4 National Insurance. Set aside more than you think you need in year one: the first bill arrives with a payment on account attached.
Why is my first 31 January tax bill so much bigger than expected?: Because you pay one and a half years of tax at once. The balancing payment for the year just ended is due, and the first payment on account towards the current year is due on the same day. On the example above that turns £25,733 into £38,599. The second payment on account follows that July.
Do payments on account apply to me?: They apply if your income tax plus Class 4 National Insurance for the year exceeds £1,000. Student loan repayments are excluded from the test and from the instalments themselves. Where they apply, each instalment is 50% of that combined figure.
How is a locum GP's NHS pension contribution tier decided?: 90% of your gross fee is pensionable. That pensionable pay is then annualised — scaled up over your days of pensionable service to what a full year would have been — and the tier is read off the annualised figure, not off what you actually earned. In the example above, £79,380 of pensionable pay across 248 days annualises to £116,829, which lands in the 12.5% tier. Starting part way through a year, or working irregular sessions, can therefore cost you a higher tier on the same money.
Does paying into the NHS pension reduce my tax bill?: It reduces your income tax at your marginal rate, capped at the income tax actually due. It does not reduce Class 4 National Insurance, because a pension contribution is not a trading expense, and it does not reduce the student loan repayment. The contribution is also cash leaving your account, so your total outgoings rise even though your tax falls — which is why this calculator shows the tax set-aside and total money out as two separate percentages.
Does it work if I pay Scottish income tax?: Yes for the tax. Scottish rates and bands, including the advanced and top rates, are applied to the income tax calculation. The NHS pension side uses the England, Wales and Northern Ireland contribution tiers, so if you are in the SPPA scheme treat the pension contribution as indicative and check the SPPA tiers.

Sources

Checked 10 August 2026, against 2026/27 rates. Rates and factors change — the primary source wins if it disagrees with anything here.

Self Assessment tax returns — GOV.UK
Understand your Self Assessment bill — payments on account — GOV.UK
Self-employed National Insurance rates — GOV.UK
Repaying your student loan — GOV.UK
NHS Pension Scheme member contributions — NHS Employers — tiers and the locum pensionable fraction
NHS Pensions member hub — NHSBSA — locum forms and annualisation

Read the guide

GP Locum Tax Guide

Every deduction that comes out of a newly qualified locum's fees — tax, Class 4 NI, student loan, pension, expenses and the first 31 January.

Read guide →

Locum GP Pension Guide

Forms A and B, the 90% rule, the 10-week deadline, and the annualisation traps that cost locums pension.

Read guide →

Annual Allowance Calculator

Work out your annual allowance charge — the taper with its workings shown, carry forward, the band-by-band charge, Scheme Pays and the tax return boxes.

Open tool →