Tax on a zero-hour contract works through PAYE in exactly the same way it does for a salaried employee: your employer deducts income tax and National Insurance from your gross pay before it reaches you. The catch is that your hours vary, so your deductions vary with them, and a busy fortnight followed by a quiet one can leave you paying more tax across the year than you actually owe. Anything overpaid is reclaimable after the tax year ends on 5 April.
How PAYE Works on Variable Hours
A zero-hour contract means your employer is not required to offer a minimum number of hours, and you are not required to accept the shifts offered.1Acas. Zero-hours Contracts For tax purposes, HMRC still treats you as an employee as long as your employer controls when, where, and how the work is done. That means your employer is responsible for deducting income tax and National Insurance before paying you.2GOV.UK. Contract Types and Employer Responsibilities – Zero-hours Contracts You do not file a self-assessment return unless you also have self-employed income on the side.
PAYE recalculates each time you are paid, based on what you earned that period. A big week produces big deductions; a light week may produce none. On a cumulative basis, the system tries to smooth this out across the tax year, but the projection can still overshoot during high-earning stretches. That is the main reason zero-hour workers commonly finish the year having overpaid.
Income Tax: What Comes Off and When
The personal allowance lets you earn £12,570 in the tax year before any income tax applies. This figure is frozen through at least 2030/31.3GOV.UK. Income Tax Rates and Allowances for Current and Previous Tax Years If your total earnings from all sources stay below that, you owe no income tax at all.
Above the allowance, tax applies in bands:
- Basic rate of 20% on taxable income from £12,571 to £50,270
- Higher rate of 40% on taxable income from £50,271 to £125,140
- Additional rate of 45% on taxable income above £125,140
The bands apply to your total annual income, not the earnings from any single job.4GOV.UK. Income Tax Rates and Personal Allowances The awkward part for zero-hour workers is that PAYE projects each period’s earnings across the full year. Earn £600 in a single week and the system taxes you as though you will earn £31,200 for the year. Earn £100 the next week and it adjusts back down. In principle the adjustments balance out; in practice, an interruption to that cumulative view is what causes lasting overpayment.
National Insurance on Irregular Pay
Class 1 National Insurance comes off your pay alongside income tax. For 2026/27 the key figures are:
- Lower Earnings Limit: £129 per week. Weeks where you earn at least this amount count toward your state pension record even though nothing is deducted.
- Primary Threshold: £242 per week (£1,048 per month). You start paying NI on earnings above this point.
- 8% on earnings between the Primary Threshold and £967 per week.
- 2% on earnings above £967 per week.
These thresholds are assessed per pay period, not annually.5GOV.UK. Rates and Thresholds for Employers 2026 to 2027 Earn £300 in a week and you pay 8% on the £58 above the threshold, roughly £4.64. Earn £200 and you pay nothing. Unlike income tax, NI is not reconciled at year-end, so a big week is not offset by a quiet one.
The Tax Code on Your Payslip
Your tax code tells your employer how much of your pay is tax-free each period. It is set by HMRC, not your employer, and it appears on every payslip. The codes zero-hour workers see most often are:
- 1257L, the standard code for someone entitled to the full personal allowance.
- BR, meaning every pound from this job is taxed at 20% with no tax-free portion. Common on a second job.
- 0T, meaning no personal allowance is applied at all. Often assigned when HMRC does not have enough information about you.
You can check and update your code through the “Check your Income Tax” service on GOV.UK or by contacting HMRC directly.6GOV.UK. Tax Codes – What Your Tax Code Means If a change is needed, HMRC updates your employer within 15 working days.7GOV.UK. Tax Codes – If You Think Your Tax Code Is Wrong
Emergency Tax Codes and Why They Hurt
Codes ending in W1 or M1 are emergency codes. They tell your employer to tax each pay period in isolation instead of cumulatively.6GOV.UK. Tax Codes – What Your Tax Code Means Under normal cumulative PAYE, the system looks at what you have earned and paid across the tax year so far and adjusts each payslip to keep the running total right. An emergency code ignores that history and treats every payment as if it were the first week or month of the year.8GOV.UK. PAYE Manual – PAYE11090 With no history to draw on, no refund gets built into a quiet week’s payslip, so overpayment becomes almost automatic.
Emergency codes usually appear when your new employer does not have your P45 and you have not filled in a starter checklist. Handing over the P45 or completing the checklist normally fixes it. If your code still looks wrong after a few weeks in a new job, HMRC asks you to wait 35 days for your new details to reach their system before getting in touch.7GOV.UK. Tax Codes – If You Think Your Tax Code Is Wrong
If You Work More Than One Zero-Hour Job
Where you hold two or more contracts, HMRC normally allocates the full £12,570 personal allowance to one job — usually the higher-paying one — and puts the others on BR, so every pound from those is taxed at 20% from the first penny.4GOV.UK. Income Tax Rates and Personal Allowances That prevents the same allowance being used twice, which would otherwise leave you with a bill later.
The setup falls short when your “main” job goes quiet and a “second” job picks up. You end up paying 20% on earnings that your unused allowance could have covered. You can ask HMRC to split the personal allowance across employers, which may reduce over-deduction during the year.9GOV.UK. How Tax Works If You Have More Than One Job Your total tax bill for the year is the same either way; this is about cash flow, not the final figure. Splitting can itself misfire if one job’s income drops unexpectedly, so it is not a universal fix.
Whatever the arrangement, keep records from every employer. Each job produces its own payslips and P60, and the combined picture is your responsibility.
Claiming Back Overpaid Tax
Overpayment is common on zero-hour work, especially if you had an emergency code for part of the year, earned nothing for several months, or stopped working before 5 April. After the tax year ends, HMRC compares your total earnings against total tax deducted and sends a P800 letter if there is a mismatch.10GOV.UK. Tax Overpayments and Underpayments If you are owed a refund, the P800 will tell you which of two routes applies:
- Online claim: request a bank transfer using the reference on your P800 and your National Insurance number, with the money arriving within 5 working days.
- Automatic cheque: arrives within 14 days of the letter date, no action required.
You can also claim through your personal tax account or the HMRC app.11GOV.UK. Tax Overpayments and Underpayments – If You’re Due a Refund
Your P60, which your employer must issue after the end of each tax year, shows total pay and total tax deducted for that employment.12GOV.UK. P45, P60 and P11D Forms – P60 If you held multiple jobs, you get a separate P60 from each. Keep them all. They are your evidence if the P800 figures look wrong, or if no reconciliation arrives and you need to prompt HMRC yourself.
Pension Auto-Enrolment: Not Tax, But It Comes Off Your Pay
One deduction that surprises many zero-hour workers is not a tax. Your employer must auto-enrol you into a workplace pension the first time your earnings hit £192 per week (or £833 per month) in a single pay period, provided you are aged between 22 and state pension age.13The Pensions Regulator. Staff Employed on Irregular Hours or Incomes Irregular hours do not exempt your employer from this duty.
The minimum employee contribution is typically 5% of qualifying earnings, with the employer adding at least 3%. Contributions get tax relief because they come out before income tax is applied. You have the right to opt out within one month of being enrolled and receive a full refund of what has been taken. If you stay opted out, your employer must re-enrol you roughly every three years.