Most people's income tax only works one way: one employer, one tax code, and a payslip that is right more or less every month. With two jobs, two separate payrolls are each working out your deductions without seeing the other. The calculator above shows the combined result for 2026/27. This guide explains the mechanics behind it, including one way two jobs can work in your favour.
How your tax codes are split
You only get one Personal Allowance, £12,570 for most people, and HMRC gives it to whichever job it treats as your main one. That job normally has a code like 1257L. The second job usually gets BR, which taxes every pound at the basic rate of 20%, or D0 if the second job would push your combined income above £50,270, which taxes every pound at 40%.
For most people this works out right over the year. Where it goes wrong is when the main job pays less than the allowance. If you earn £8,000 in one job and £15,000 in another, putting the whole allowance on the first job wastes about £4,500 of it, and the BR code on the second job then over-taxes you. You can ask HMRC to split your allowance between the two jobs so each code matches what you actually earn there. You can do this online through your personal tax account, and the change shows in the next payslip.
The National Insurance advantage
Income tax looks at your total income. National Insurance doesn't. Each employer works it out separately, and each job gets its own threshold of £12,570 a year. That means two moderate jobs can pay noticeably less National Insurance than one job with the same total pay.
Take Chris, who works two part-time jobs paying £20,000 each. Each employer charges 8% on the £7,430 above the threshold, which is about £594 per job, or £1,189 in total. A single full-time job paying £40,000 would cost £2,194 in National Insurance, about £1,006 more. The income tax is the same either way, because the allowance is only used once. Two jobs with the same employer are normally added together for National Insurance, so the advantage only applies to genuinely separate employers.
Pensions and student loans
Auto-enrolment is assessed separately for each job too. An employer only has to enrol you automatically if your earnings with them are over £10,000 a year, so someone with two jobs paying £9,000 each may not be enrolled in either. You can still ask to join, and if your earnings in a job are above the lower qualifying limit the employer must contribute. It is one of the most commonly missed benefits for people combining part-time roles.
Student loan deductions work like National Insurance, job by job against each payroll's share of the threshold. If neither job is above it, neither deducts anything, even if your combined income is. You may then owe repayments through Self Assessment or a later adjustment, so it's worth putting money aside rather than treating the gap as a saving.
Common mistakes
The most common mistake is assuming the second job is "taxed more". It isn't. A BR code simply applies the basic rate from the first pound, because your allowance is already being used elsewhere. Another is not checking the codes when a job starts or ends: if you leave your main job and your second job keeps its BR code, you'll pay tax on income that should be tax-free until HMRC catches up. Finally, if a second job takes your total income above £50,270, make sure one of the codes reflects it, or you could face a tax bill after the year ends.
Next steps
Enter both salaries above to see your combined take-home and the deductions in each job. If you're choosing between a second job and extra hours in your main one, the compare two salaries calculator shows the full-time equivalent side by side, and the hourly wage calculator converts shift rates into annual figures.