Second Job Tax UK: How a Second Income Is Taxed in 2026/27

How is a second job taxed in the UK? You get one Personal Allowance a year, and HMRC usually sets it against your main job. Your second income is then taxed from the first pound: a second employed job normally carries a BR tax code that charges 20% on all of it, and a self-employed side income is taxed through Self Assessment once it clears £1,000. National Insurance follows separate rules again, worked out one job at a time. This guide covers both routes, the tax codes, the threshold that pulls you into a tax return, and a worked 2026/27 example.

The mechanics split depending on whether your second income comes from an employer or from your own trade, because the two are taxed through different systems. If your side income is self-employment, the profit you get taxed on is what you earned minus what you spent, so clean records set the number. Our expense tracker and the guide to the £1,000 trading allowance both feed into that figure.

You get one Personal Allowance, and it sits on your main job

For the 2026/27 tax year the standard Personal Allowance is £12,570, the slice of income you pay no tax on. The rate bands above it are 20% from £12,571 to £50,270, 40% from £50,271 to £125,140, and 45% above that, per HMRC's Income Tax rates and allowances. The allowance shrinks by £1 for every £2 you earn over £100,000 and disappears at £125,140.

The catch with a second income is in one line of HMRC's guidance on more than one job: "You only get one Personal Allowance for each tax year even if you have income from more than one job." HMRC usually allocates that allowance to the job that pays you the most. Your main employment spends the tax-free slice, so the second income has none left and is taxed from the first pound it pays.

That is why a second job can feel taxed to the hilt. The money is not taxed at a penalty rate. It lands on top of income that already used your allowance, so it starts at 20% rather than at zero.

Second job tax codes: BR, D0 and D1

A tax code tells each employer how much tax to deduct. Your main job usually carries 1257L, which hands it the full £12,570 allowance. Your second job gets a different code that applies no allowance, because the allowance is already in use elsewhere. HMRC's page on what your tax code means sets out the ones you are likely to see.

Which code lands on your second job depends on your total income. If your main job pays £30,000, a second job on a BR code is about right, since everything still sits in the basic-rate band. If your main job already pays £55,000, a BR second job would under-tax you, and HMRC will usually move it to D0 so the second income is taxed at 40%. HMRC issues these codes automatically from the payroll data your employers report, so a code can lag reality when your pay changes. You can check and correct it in your personal tax account.

An employed second job and a self-employed side income are taxed differently

Before the numbers, sort your second income into one of two boxes, because they run through different machinery.

An employed second job has an employer who operates PAYE. That employer applies the BR (or D0) code, deducts the tax before you are paid, and handles National Insurance on that job. In most cases you do nothing extra, and if your codes are right, the tax is settled by payday.

A self-employed side income has no employer to deduct anything. Freelancing, selling online, tutoring, delivery and gig work all fall here. You report the income yourself on a Self Assessment tax return, work out the profit, and pay the tax and any National Insurance after the tax year ends. This is the route that needs record-keeping, because you are the one proving the numbers.

When a side income means you must file a Self Assessment return

The dividing line for a self-employed side income is £1,000 of gross income in a tax year, the trading allowance. HMRC's rule is plain: "If your annual gross trading income is £1,000 or less, from one or more trades you may not have to tell HMRC," and "You must tell HMRC if you have gross trading income over £1,000." Gross means the money in before you take off any costs.

Clear £1,000 and you register for Self Assessment. The deadline to register is 5 October after the end of the tax year in which the income arose, and our guides to registering as a sole trader and the Self Assessment deadlines walk the timeline from first sale to first return. Registering late is a failure to notify, so the 5 October date is worth a diary entry.

Once you file, you choose between the flat £1,000 trading allowance and your actual expenses, and you cannot take both. The crossover is exact: if your costs for the year came to less than £1,000, the allowance leaves a lower profit; once your costs pass £1,000, claiming them wins. The trading allowance guide does that maths in both directions.

National Insurance on a second income

Income tax pools your income and taxes the total. National Insurance does not. It is worked out one job at a time, which produces a quirk worth knowing.

For an employed second job, Class 1 National Insurance uses each job's own threshold. HMRC's rates charge 8% on weekly earnings between £242 and £967, then 2% above £967, and each employment starts its own count from £242 a week. A second job paying under £242 a week (about £12,570 a year) pays no National Insurance at all, even when your combined pay across both jobs is well over the threshold.

For a self-employed side income, you pay Class 4 and Class 2 through Self Assessment. The self-employed rates set Class 4 at 6% on profits between £12,570 and £50,270 and 2% above £50,270. Class 2 is treated as paid once your profits pass the Small Profits Threshold of £7,105, so there is nothing more to pay; below £7,105 you can pay Class 2 voluntarily at £3.65 a week to keep the year on your State Pension record. Our self-employed National Insurance guide covers how both classes appear on your return.

Worked example: a £38,000 employee with a £6,000 side income

Take an employee earning £38,000 on a 1257L code, who also earns £6,000 freelancing with £1,200 of allowable costs.

The job. The £12,570 allowance sits here, leaving £25,430 taxed at 20%, which is £5,086. Class 1 National Insurance of roughly £2,033 comes off through payroll. All of it is handled before payday.

The side income. Costs of £1,200 top £1,000, so claiming actual expenses beats the trading allowance. Profit is £6,000 minus £1,200, which is £4,800. The allowance is already used on the job, and total income of £42,800 still sits inside the basic-rate band, so the £4,800 is taxed at 20%, which is £960 due through Self Assessment.

NI on the side income. Profit of £4,800 is below the £12,570 Class 4 threshold, so there is no Class 4 to pay. It is also below the £7,105 Small Profits Threshold, so no Class 2 is due either, though £3.65 a week voluntarily would protect the pension year. National Insurance on the side income is nil.

So the £4,800 profit adds £960 to the January tax bill and nothing in National Insurance. Claiming the £1,200 of costs rather than the £1,000 allowance shaved £200 off the taxable profit, worth £40 in tax, which is why the receipts matter.

Two employed jobs work out the same in total as one combined job, which surprises people who expect a penalty. A £30,000 main job and a £10,000 second job produce £3,486 on the main job (£17,430 taxed at 20%) and £2,000 on the second job (all £10,000 at the BR rate), which is £5,486. One £40,000 job would tax £27,430 at 20%, also £5,486. The second job's £10,000 pays no Class 1 National Insurance, because £192 a week is under the £242 threshold.

How SparkReceipt fits

A self-employed side income is taxed on profit, so every receipt you lose is profit you are taxed on twice over. SparkReceipt scans receipts and sorts them into categories as you go, so the year's costs are captured before the thermal paper fades, and it turns them into a tax-ready expense report behind an accurate profit figure. It does not file your Self Assessment return or set your tax code, and it will not fix a wrong code from an employer. What it does is keep the records that make the profit figure right, which is the number your side-income tax is built on. See what counts as an allowable expense, or start on pricing.

Frequently asked questions

Do I pay more tax overall by taking a second job?

No. Your total tax is the same as if a single job paid the combined amount, because Income Tax pools all your income. A second job feels heavily taxed only because it carries none of the tax-free Personal Allowance, which your main job has already used. If your tax codes are wrong you can over- or under-pay in-year and settle the difference with HMRC afterwards.

Why is my whole second job taxed at 20% with nothing tax-free?

Because it is on a BR code. Your Personal Allowance is attached to your main job, so the second job applies no allowance and taxes every pound at the basic rate. If your main income already reaches the higher-rate band, HMRC will usually issue a D0 code and tax the second job at 40%.

Do I pay National Insurance on both jobs?

Possibly not. Class 1 National Insurance is worked out separately for each employment, each with its own £242-a-week starting point. A second job paying under that threshold pays no National Insurance, even if your total earnings across both jobs are much higher.

I earned £500 from a side hustle. Do I need a tax return?

Not on that alone. Gross trading income of £1,000 or less falls under the trading allowance, and HMRC says you may not have to tell them, unless another reason puts you into Self Assessment. Pass £1,000 and you must register.

Can I use the trading allowance and claim expenses?

No, you take one or the other. If your allowable costs for the year are under £1,000, the flat allowance leaves a lower profit; once your costs pass £1,000, claiming the actual figures wins.

Key takeaways

• You get one Personal Allowance, and HMRC sets it against your highest-paying job, so a second income is usually taxed from the first pound.
• A second employed job normally carries a BR code taxing all of it at 20%, moving to D0 (40%) once your main job fills the basic-rate band.
• A self-employed side income goes through Self Assessment once gross income passes £1,000; register by 5 October after the tax year.
• National Insurance is worked out one job at a time, so a second job under £242 a week pays no Class 1, and a side profit under £7,105 pays no Class 2.
• Two jobs pay the same total Income Tax as one combined job, so the second income is not penalised, only stripped of the tax-free slice.
• For a self-employed side income the tax rides on profit, so tracked receipts and expenses are what keep the figure, and the bill, accurate.