Second Job Tax Calculator United Kingdom

Tax on a second job works differently from your main job. Because your personal allowance is already used by the first job, the second is usually taxed from the first pound, while National Insurance is worked out on each job separately. This calculator shows what you will keep from a second job in 2026/27.

Income Tax: no second personal allowance

You get one personal allowance, normally applied to your main job through your tax code. The second job’s code is usually BR (basic rate), D0 (higher rate) or D1 (additional rate), so every pound of it is taxed at that rate with no tax-free slice. The second job sits on top of the first and is taxed at your marginal rate. If it takes your total income over the £50,270 higher rate threshold, part of it is taxed at 40%. The calculator works this out as the extra Income Tax the second job adds to your total.

National Insurance: each job has its own threshold

National Insurance is charged per employment, and each job gets its own primary threshold before NI is due. A second job paying less than the threshold pays no National Insurance, even though every pound is taxed for Income Tax, so a small second job can be efficient on NI while still being fully taxed. The calculator works out NI on the second job’s pay alone.

Getting your tax code right

Tax codes split your allowance, so check they are correct. If HMRC applies your personal allowance to the lower-paid job, you could pay too much tax during the year, though it usually balances out. You can ask HMRC to move your allowance to the job that pays more, or split it, so your deductions during the year better match what you owe. The calculator shows the correct overall tax on the second job whatever the code.

A worked example

Someone earning £30,000 in their main job who takes a £10,000 second job pays 20% Income Tax on the whole £10,000, £2,000, but no National Insurance, because £10,000 is below the second job’s own NI threshold. They keep £8,000. With a £20,000 second job, NI applies to the part above the threshold, about £594, alongside £4,000 of tax. If the main job pays £45,000, a £15,000 second job is partly taxed at 40%: £4,946 of Income Tax and about £194 of NI.

How to use the calculator

Enter your first job’s salary and your second job’s pay. The result shows the Income Tax and National Insurance on the second job, the total deducted, your take-home from it each year and month, and the effective rate. Use it to decide whether a second job is worth it, to check your tax code, or to see where the second job starts paying NI.

Common mistakes with a second job

• Believing a second job is taxed at a penalty rate. Every pound is taxed at your marginal rate, which feels harsh only because your personal allowance is already used.
• Never checking the second job’s tax code. If HMRC has your details wrong you can overpay or underpay during the year.
• Forgetting that NI is charged per employment. Two modest jobs can pay less NI together than one job with the same total pay, which helps you but can also leave gaps in your NI record.
• Overlooking the combined total. Two jobs together can take you over the £50,270 higher rate threshold, or past £100,000 where the personal allowance starts to taper.
• Using this tool for self-employed income. That follows different rules, with Class 4 NI and a Self Assessment return, so use the self-employed calculator instead.

What happens at the end of the tax year

PAYE deducts tax job by job, so the deductions across two employments do not always add up to the right total. After the tax year HMRC reconciles your combined income and sends a P800 calculation if you have overpaid or underpaid, which can mean a refund or a bill. Keep both P60s and check that the tax taken matches what you owe on your total income. If the lower-paid job keeps taking your allowance, ask HMRC to move or split it towards the higher-paid job. The calculator shows the correct overall position, so you can see whether your payslips are about right.

Assumptions and limitations

This is a planning estimate. It uses the 2026/27 Income Tax bands and Class 1 employee NI, applies the personal allowance taper, and assumes the personal allowance is fully used by the first job. It treats each job’s NI separately, as the rules require. It does not model student loan deductions, pension contributions, the in-year effect of a specific tax code, Scottish Income Tax bands or self-employed second income. The rates are stored as parameters sourced from HMRC and reviewed each tax year.

About This Second Job Tax Calculator

Use this second job tax calculator to get an instant, accurate estimate. The figures follow official GOV.UK guidance and every rate and threshold is kept up to date for 2026. Adjust the inputs above to match your situation, or browse all our calculators to plan your next step.