Tax on two UK employments combined.
Net annual take-home
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Combined PAYE
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Combined NI
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How HMRC splits your allowance across two payslips
When you hold two jobs, only one of them can carry your tax-free Personal Allowance. HMRC normally attaches the full £12,570 to whichever employment it treats as your main one, giving that payroll a 1257L code, and puts the second job on a BR code so every pound there is taxed at 20 percent from the first penny. That is exactly why a second job can feel like it is taxed harder: it is not penalised, it simply has no allowance left to use, because the allowance is already working on your main wage.
This calculator takes a cleaner view than two separate payslips can. It adds both salaries, applies a single Personal Allowance to the combined figure, and runs the total through the income tax bands, so the income tax it shows is what you genuinely owe for the year once everything is reconciled. If your two BR-coded payslips deducted slightly the wrong amount in real time, HMRC squares it up after 5 April, and the figure here is the destination that reconciliation lands on.
The National Insurance quirk most people get wrong
Income tax pools across jobs, but National Insurance does not. Each employer applies the NI Primary Threshold to its own payroll independently, so each job gets its own slice of earnings below £12,570 that pays no NI at all. With two modest jobs, that means two tax-free NI bands instead of one, and you usually pay less employee NI than a single person earning the same total. The on-screen note flags the opposite risk, and both can be true depending on the numbers, so it is worth understanding when each applies.
You only overpay NI when both jobs are large. National Insurance charges 8 percent on earnings between £12,570 and the Upper Earnings Limit of £50,270, then just 2 percent above it. A single high earner crosses that £50,270 ceiling once. Someone splitting the same income across two well-paid jobs can be charged the full 8 percent twice on bands that a single earner would only pay 2 percent on. That is the overpayment case, and HMRC will refund the excess above the annual maximum if you claim it.
A £35,000 plus £15,000 split, line by line
Take the default inputs: a £35,000 main job and a £15,000 second job, £50,000 in total. The Personal Allowance is well below the £100,000 taper threshold, so the full £12,570 applies once to the combined income.
| Line | Amount |
|---|---|
| Combined salary | £50,000 |
| Less Personal Allowance | £12,570 |
| Taxable income at 20 percent | £37,430 → £7,486 tax |
| NI on main job (£35,000 over the £12,570 threshold, at 8 percent) | £1,794.40 |
| NI on second job (£15,000 over its own £12,570 threshold, at 8 percent) | £194.40 |
| Combined NI | £1,989 |
| Net annual take-home | £40,525 |
The telling figure is the NI. Because each job got its own £12,570 threshold, the combined NI is £1,989. A single person earning £50,000 in one job would pay £2,994, since only one threshold shields them. The chart compares the two, using the same NI formula on the same total income.
When two jobs actually cost you more
The NI saving flips into a cost once both jobs are substantial. Picture two jobs of £40,000 each: each crosses the £12,570 threshold and pays 8 percent NI up to £50,270, but neither alone reaches the ceiling, so almost none of your income enjoys the cheaper 2 percent rate that a single £80,000 earner would benefit from. That is the scenario the HMRC annual-maximum NI rule exists for, and you can reclaim the excess after the year ends. The other common trap is income tax: if your main job already uses the basic-rate band, the second job's earnings can quietly tip you into the 40 percent higher rate, which BR coding at 20 percent will not collect, leaving a bill at reconciliation.
Should I ask HMRC to move my allowance to the bigger job?
Usually yes. If your main job does not use the whole £12,570, HMRC can split the allowance so part of it lands on the second job through a custom code rather than a flat BR. The simplest fix is to check your Personal Tax Account and make sure the larger, more stable job holds the allowance, so you are not handing too much to a job you might leave.
Will a second job push my whole income into a higher tax band?
Only the part above each threshold is taxed at the higher rate, never your entire income. But a second job stacks on top of the first, so it is the marginal pounds that get hit. If the combined total crosses £50,270 of taxable income, those extra pounds attract 40 percent, which is why higher earners taking on side work often see less of it than they expect.