How to Fill in a Self Assessment Tax Return for Gig Workers (2025/26)
How to Fill in a Self Assessment Tax Return for Gig Workers
Over 750,000 people in the UK now work in the gig economy, and every single one who earns more than £1,000 from self-employment must file a Self Assessment tax return with HMRC. Yet for many delivery drivers, this annual obligation feels like navigating a minefield blindfolded.
If you drive for Uber Eats, Deliveroo, Just Eat, Amazon Flex, or any other platform, this guide walks you through every box of the SA100 and SA103S forms — in plain English, with real numbers, so you can file accurately and on time.
Who Needs to File a Self Assessment?
You must register for Self Assessment and file a tax return if any of these apply:
- You earned more than £1,000 from self-employment (the Trading Allowance threshold)
- You are a partner in a business partnership
- You need to claim tax relief on expenses above the Trading Allowance
- HMRC has sent you a notice to file
Even if your gig income is below £1,000, filing can be beneficial if you have expenses that exceed that amount — you could reduce your overall tax bill. Try our free tax estimate tool to see whether filing makes financial sense for you.
Step 1: Register with HMRC (If You Haven't Already)
Before you can file, you need a Unique Taxpayer Reference (UTR) number. If you haven't registered:
- Go to gov.uk/register-for-self-assessment
- Select "Self-employed" or "Not self-employed" depending on your situation
- Complete the online form — you'll need your National Insurance number
- HMRC will post your UTR within 10 working days (or 21 days if abroad)
Important: You must register by 5 October following the end of the tax year in which you started self-employment. Miss this and you risk a penalty.
Step 2: Gather Your Records
Before opening the tax return, collect everything you need:
| Document | Where to Find It |
|---|---|
| Platform earnings statements | Uber Eats app → Earnings tab; Deliveroo → Invoice section |
| P60 or P45 (if employed too) | From your employer, usually issued by 31 May |
| Expense receipts | Your records — fuel, phone, insurance, equipment |
| Mileage log | Your tracking app or manual log |
| Bank statements | Your bank — useful for cross-referencing income |
| Previous year's tax return | HMRC online account or your records |
Step 3: The SA100 — Main Tax Return
The SA100 is the main form. Key sections for gig workers:
- Box 1-4 (Personal details): Your name, UTR, NI number, and date of birth
- Employment section: If you also have a PAYE job, enter your P60 figures here — your gross pay and tax deducted
- Self-employment section: Tick the box to say you have self-employment income, which triggers the SA103S supplementary page
Step 4: The SA103S — Self-Employment (Short)
This is where your gig income lives. Most delivery drivers use the "short" version (SA103S) because turnover is under £85,000.
Box 9 — Turnover (Your Total Gig Income)
Enter the total gross income from all gig platforms combined. This is the amount before any deductions. For example:
- Uber Eats earnings: £8,200
- Deliveroo earnings: £3,400
- Amazon Flex earnings: £1,800
- Total Turnover (Box 9): £13,400
Box 10 — Allowable Expenses
Here you claim your business costs. You have two options:
- Option A — Trading Allowance: Claim a flat £1,000 deduction (no receipts needed). Only use this if your actual expenses are less than £1,000.
- Option B — Actual Expenses: Claim the real cost of running your delivery business. This includes fuel, vehicle insurance (business portion), phone bill (business portion), thermal bags, and more.
Most active drivers save more with actual expenses or the simplified mileage method (45p per mile for the first 10,000 miles). Use our Uber Eats tax calculator to compare which method saves you more.
Box 29 — Net Profit
This is calculated automatically: Turnover minus Allowable Expenses. Using our example:
- Turnover: £13,400
- Mileage claim (8,000 miles × 45p): £3,600
- Net Profit: £9,800
Step 5: Calculate Your Tax
Your net profit is added to any employment income to work out your total taxable income. Here's a worked example:
| Income Source | Amount |
|---|---|
| PAYE Salary | £25,000 |
| Gig Net Profit | £9,800 |
| Total Income | £34,800 |
| Personal Allowance | -£12,570 |
| Taxable Income | £22,230 |
Income Tax at 20% on £22,230 = £4,446. Your employer already deducted tax on the first £25,000 via PAYE, so you only owe additional tax on the gig profit portion. Don't forget Class 4 National Insurance at 6% on profits between £12,570 and £50,270.
Rather than doing this manually, use our free calculator to get an instant, accurate breakdown.
Step 6: Submit and Pay
- Online deadline: 31 January following the end of the tax year
- Paper deadline: 31 October (not recommended — slower and more error-prone)
- Payment deadline: 31 January (same as online filing deadline)
You can pay via direct debit, bank transfer, or even at the Post Office. If your bill is over £1,000, HMRC may ask for Payments on Account — two advance payments towards next year's bill.
Common Mistakes to Avoid
- Mixing up gross and net platform earnings: Always use the gross figure (before platform fees) as your turnover
- Forgetting tips: Cash and in-app tips are taxable income
- Claiming personal mileage: Only business miles count — commuting to a regular depot doesn't qualify
- Missing the deadline: A £100 penalty applies immediately, rising to £10/day after 3 months
- Not claiming enough expenses: Many drivers leave money on the table by not tracking mileage properly
Frequently Asked Questions
Do I need an accountant to file my Self Assessment?
No. HMRC's online system is designed for individuals. However, if your tax situation is complex (e.g., multiple income sources, capital gains), an accountant can be worthwhile. Our free calculator can handle the numbers for most gig workers.
What happens if I file late?
You'll receive an automatic £100 penalty, even if you owe no tax. After 3 months, daily penalties of £10 apply (up to £900). After 6 months, an additional 5% of tax owed is charged.
Can I amend a tax return after submitting?
Yes. You have 12 months from the filing deadline to amend your return online.
Do I report each platform separately?
No. You combine all self-employment income into one total on the SA103S form.
What if I made a loss?
You can carry the loss forward to offset against future profits, or carry it back against the previous year's income in some cases.
Conclusion
Filing a Self Assessment doesn't have to be stressful. With the right records and a clear understanding of each box, you can complete your return in under an hour. The key is preparation — gather your earnings statements, track your mileage, and know which expense method saves you the most.
Not sure how much you owe? Try our free gig worker tax calculator to get an instant estimate before you file.