Gig work alongside a PAYE job: tax made simple

Summary

If you do gig work alongside a PAYE job in 2025-26, HMRC adds everything together and taxes your gig profit at whatever band your total income sits in: 20%, 40% or 45%.

You keep your PAYE job exactly as it is, but you must usually register for Self Assessment, pay Class 4 National Insurance on gig profits, and your student loan repayments are recalculated on the combined income.

There is no law forcing you to tell your boss about your Uber or Deliveroo shifts, but your contract might have rules on second jobs, and TikTok "side-hustle hacks" telling you HMRC will never see gig income in 2025-26 are nonsense now that platforms report data directly to HMRC.

Key facts (UK 2025-26)

• Tax year: 6 April 2025 to 5 April 2026.
• PAYE job stays on PAYE. Employer deducts income tax and Class 1 NI using your tax code.
• Gig work (Uber, Deliveroo, Amazon Flex, Just Eat, Stuart, Gophr, private hire) is normally treated as self-employment, so profits are taxed through Self Assessment as trading income.
• Income tax bands 2025-26 (England, Wales, NI): personal allowance £12,570, 20% on taxable income £12,571 to £50,270, 40% on £50,271 to £125,140, 45% above £125,140.
• Class 4 NI 2025-26 on gig profits:
  • 6% on profits between £12,570 and £50,270.
  • 2% on profits above £50,270.
• Class 2 NI 2025-26: small profits threshold £6,845; profits at or above this are treated as having paid Class 2; below this you can pay voluntary Class 2 at £3.50 a week to protect your pension record.
• Trading allowance: first £1,000 of gross trading income (across all gigs combined) can be covered by the trading allowance if you meet the conditions; over £1,000 gross, you must register and file.
• Student loan 2025-26: you repay 9% (Plans 1, 2, 4, 5) or 6% (Postgrad) of income above your plan's threshold, based on total income (employment + self-employment) through Self Assessment.
• Platforms now report income to HMRC under the UK's DAC7-style digital-platform reporting rules from 2024 onwards, so HMRC can see a lot of gig income even if you never tell them.

Legislation, case law, regulation

• Income Tax (Earnings and Pensions) Act 2003 (ITEPA 2003): governs PAYE, employment income and tax codes for your PAYE job.
• Income Tax (Trading and Other Income) Act 2005 (ITTOIA 2005): defines trading income (self-employment), how profits are worked out, and underpins the £1,000 trading allowance.
• Income Tax Act 2007: sets the personal allowance and tax-band framework used for 2025-26.
• Social Security Contributions and Benefits Act 1992 and NIC regulations: establish Class 1 (employment), Class 2 and Class 4 (self-employed) National Insurance.
• Taxes Management Act 1970: the core Self Assessment law; explains who must file and how HMRC can adjust tax codes for underpaid tax from extra income.
• Student Loans (Repayment) Regulations: set 9%/6% repayment rates and thresholds by plan; HMRC's and LITRG's 2025-26 guidance explain how Self Assessment uses combined income.
• OECD / DAC7-style platform-reporting rules and UK implementing regulations: require platforms to report seller/worker income data to HMRC from 2024.

How it actually works

1. Tax bands, gig income is taxed on top

When you have both PAYE income and gig profits in 2025-26:

HMRC adds up all your taxable income:

• wages and benefits from your PAYE job (after deducting any tax-free parts);
• gig profits (income minus expenses);
• any other taxable income.

It applies the 2025-26 bands:

• First £12,570: 0% (personal allowance).
• £12,571 to £50,270: 20%.
• Above that: 40% or 45% depending on level.

So if your PAYE job already uses up your £12,570 personal allowance and fills most of the basic-rate band, almost all gig profit is taxed at 20% or 40%.

2. National Insurance, Class 1 on wages, Class 4 on gig profits

Your employer deducts Class 1 NI from wages under ITEPA 2003 and NIC rules, using the 2025-26 thresholds for employees (mainly a primary threshold and upper earnings limit).

Separately, your Self Assessment calculates:

• Class 4 NI on gig profits (6% between £12,570 and £50,270, 2% above).
• Class 2 NI (treated as paid if profits are at or above £6,845, or voluntary at £3.50 a week if below that but you want a qualifying pension year).

Class 1 on wages and Class 4 on profits are separate; there is no automatic exemption just because you already pay Class 1.

3. Registering for Self Assessment while employed

You do not leave PAYE when you become self-employed on the side.

• You stay as an employee with your employer operating PAYE as usual.
• You register for Self Assessment because you now have untaxed income (gig work).

You usually need to register if:

• your total gross gig income in 2025-26 is over £1,000 (trading allowance limit); or
• HMRC tells you directly to complete a return.

Once registered:

• You file each year by 31 January 2027 for 2025-26 if filing online.

4. Filling in SA100 with both employment and self-employment

On the 2025-26 online Self Assessment (SA100 plus schedules):

Employment section:

• Enter details from your P60/P45: pay, tax deducted, benefits.

Self-employment section (SA103):

• Enter total gig income (all app payouts).
• Either claim actual expenses or use the £1,000 trading allowance as a flat deduction, not both.

The system then:

• calculates additional income tax on your combined income;
• adds Class 2 and Class 4 NI for gig profits;
• computes any extra student loan due on the total.

5. Student loans, combined income, not just your job

For 2025-26, typical thresholds are around:

• Plan 1: about £26,065, repay 9% above this.
• Plan 2: about £28,470, repay 9% above this.
• Plan 4: about £32,745, repay 9% above this.
• Plan 5: £25,000, repay 9% above this.
• Postgrad: £21,000, repay 6% above this.

Your employer's PAYE only sees your salary, but Self Assessment uses total income (salary + profits + other) to work out the real student loan due. If your employer took too little via PAYE (very common when gig work pushes you over the threshold), Self Assessment adds an extra student-loan line to your bill.

6. Do you have to tell your employer?

Legally:

• You do not have to tell your employer that you drive for Uber or ride for Deliveroo unless your contract says otherwise.

But you must check:

• Exclusivity clauses. Some contracts ban working for competing businesses or doing a second job without permission.
• Working time & safety policies. Some employers (especially driving roles) may restrict extra driving work.

If a platform deactivates you, that is their problem. If your employer finds you breached contract by moonlighting behind their back, that can become your problem.

7. Tax code adjustments

HMRC can use your tax code to collect some underpaid tax in future years:

• After you file Self Assessment, HMRC may adjust your main PAYE code so that more tax is taken from your wages the following year.
• This reduces the cash you take home from your job while reducing what you have to pay on the next 31 January.
• You can usually see and object to these changes in your Personal Tax Account if they look wrong.

8. Practical management

Best practice:

• Keep gig records separate: one spreadsheet or app showing earnings, mileage and expenses.
• Keep every P60/P45 and payslip from your job.
• Put tax, NI and loan money for gig work into a separate tax pot, because PAYE does not cover it.

Worked example

Worker in England in 2025-26, no student loan, no other income.

• PAYE job salary: £28,000.
• Gig work (Uber) profit after expenses: £8,000.

1. Income tax bands

• Total income = £28,000 + £8,000 = £36,000.
• Personal allowance: £12,570, so taxable income = £23,430.
• All of this sits in the basic-rate band (£12,571 to £50,270), so taxed at 20%.
• Income tax = 20% of £23,430 = £4,686.

How this is collected:

• Employer's PAYE already deducted tax on the £28,000 salary using a typical code (roughly):
  • Salary taxable slice = about £15,430, so PAYE = about £3,086.
• Self Assessment then charges the difference so that total income-tax reaches £4,686, so roughly £1,600 extra income tax is due because of gig profits.

2. National Insurance

Class 1 on wages (ballpark, 2025-26 thresholds for employees):

• The employer will have deducted Class 1 on £28,000 salary via PAYE (exact figure depends on thresholds and any contracted-out details).

Class 4 on gig profits:

• Gig profits: £8,000.
• Class 4 threshold: £12,570, so if this worker has no other self-employed income, profits are below the Class 4 lower profits limit and there is no Class 4 NI.

However, if this same person had £18,000 gig profit:

• Profits above £12,570 = £5,430, so Class 4 at 6% = £325.80.

Class 2 NI:

• Profits above £6,845, so Class 2 treated as paid (qualifying year), no extra weekly bill.
• Below that, they could pay voluntary Class 2 at £3.50 a week.

3. Total position (with £8,000 profit scenario)

• PAYE job income tax: roughly £3,086 already deducted.
• Gig-driven extra income tax via Self Assessment: about £1,600, making total income tax = about £4,686.
• Class 4 NI on gig profits: £0 (because profits below £12,570).
• Class 2 NI: treated as paid if profits over £6,845; otherwise optional.

Reality: that "extra £8,000" from Uber will lead to an extra four-figure bill at 31 January, even though the worker's payslips looked fine all year.

What Reddit, TikTok and forums get wrong

1. "Your gig earnings are taxed separately at 20%, like a second job." Wrong. HMRC taxes your combined income. Gig profits are simply stacked on top of wages and taxed at whatever band your total reaches (20%, 40%, 45%).

2. "If you already pay NI at work, you don't pay NI on your side gig." Wrong. You pay Class 1 on wages and Class 4 on gig profits if profits are above £12,570 in 2025-26; these are separate, and it's very normal to pay both.

3. "My employer sorts my tax so I don't need Self Assessment, even with £5k from Uber." Dangerous. GOV.UK Self Assessment guidance says people with other untaxed income (like self-employment) must file; HMRC's own posts say earning more than £1,000 through a side-hustle is a common reason to need a return.

4. "Student loan is only based on your job; side gigs don't affect it." False. LITRG and nidirect explain that Self Assessment student-loan rules use total income, including gig profits, and can add extra repayments on top of PAYE deductions.

5. "Don't declare the gig work, HMRC and SLC will never find it." Out of date. HMRC has digital-platform reporting and cross-checks; untied, LITRG and HMRC all warn that DAC7-style rules mean platform earnings are increasingly visible to HMRC.

Action steps for the reader

1. Add up your expected 2025-26 PAYE salary plus expected gig profit; see which tax band your total will land in using the 2025-26 bands.
2. If your total gig gross income is likely to be over £1,000, register for Self Assessment now rather than waiting for an HMRC nudge.
3. Start a simple gig-income spreadsheet: for each week list platform, gross income, key expenses, and mileage.
4. Check your student-loan plan and threshold, then budget 9% (or 6% for postgrad) of income above that line across both your job and gig profits.
5. Read your employment contract for second-job or exclusivity clauses before you tell colleagues about your app work on WhatsApp.
6. From your first gig payout, move a fixed percentage (for many workers 25% to 30% of gig income) into a separate tax pot to cover income tax, NI and student loans on that side of your life.

Related tools GigKiln should build

• Job-plus-gig tax estimator: takes PAYE salary and gig profit, and shows 2025-26 tax, NI and student loan impact.
• Side-gig Self Assessment checker: quick quiz that tells an employed worker if they now need to register for Self Assessment.
• Tax-code explainer: tool that reads a sample tax code and explains how HMRC is using it to collect underpaid tax from gigs.

Related guides

• "First Self Assessment for people with a job and gig work"
• "How student loans work when you have a PAYE job and gig income"
• "National Insurance when you're both employed and a gig worker"
• "What HMRC's platform-reporting rules mean if you already have a job"

Sources

Primary

• GOV.UK, Self Assessment tax returns: Overview, accessed 18 April 2026.
• GOV.UK, Working for yourself, accessed 18 April 2026.
• GOV.UK, Income Tax rates and Personal Allowances, accessed 18 April 2026.
• GOV.UK, Rates and allowances: National Insurance contributions, accessed 18 April 2026.
• GOV.UK, Self-employed National Insurance rates, accessed 18 April 2026.
• LITRG, Self Assessment: student loan repayments, accessed 18 April 2026.

Secondary

• TaxAid, Who needs to complete a Self Assessment tax return?, accessed 18 April 2026.
• LITRG, Student loan repayments, accessed 18 April 2026.
• nidirect, Repaying student loans through Self Assessment, accessed 18 April 2026.
• Crunch, Student Loan Repayment When You're Self-Employed, accessed 18 April 2026.
• HMRC social posts, Do you need to do a Self Assessment tax return?, accessed 18 April 2026.
• Taylor Wessing, Tipalti, Tax Natives, and LITRG on digital-platform reporting / DAC7 implementation, accessed 18 April 2026.