Side Hustles | Self Assessment
Your First Tax Return for a Side Hustle: The 2026 Step-by-Step Guide
You passed £1,000 of side hustle income, so a tax return is now in your future. If you have never filed one, the process is more form-filling than ordeal, and doing it early beats doing it in a January panic. Here is the whole thing, start to finish.
Not sure you actually need to file? Start with our guide to side hustle tax and the £1,000 rule, because if your gross trading income is under £1,000, or you were only selling your own belongings, you can stop reading now.
Step 1: Register for Self Assessment
Register online at GOV.UK as self-employed (sole trader). The deadline is 5 October following the end of the tax year you passed £1,000 in. HMRC posts your Unique Taxpayer Reference (UTR) within about two weeks, and you activate your online account with it. Register once; it covers every year after.
Step 2: Get Your Records Together
- Income: platform statements (Vinted, eBay, Etsy and the rest all let you download a yearly summary), invoices for freelance work, app earnings reports.
- Costs: stock purchases, postage and packaging, platform fees, materials, business mileage, phone and home-working proportions.
- Employment: your P60 (and P45 or P11D if relevant) from any day job, because the return covers all your income, not just the side hustle.
Step 3: The £1,000 Allowance or Real Expenses, Pick One
On the self-employment pages you choose: deduct the £1,000 trading allowance, or deduct your actual costs. Take whichever is larger. A reseller with £2,800 of sales and £1,900 of stock and postage costs should claim the real expenses (taxable profit £900). A freelancer with £2,800 of income and a laptop they already owned should take the allowance (taxable profit £1,800). You can switch choice each year.
Step 4: Fill In the Return
The online return asks for your employment income (straight off the P60), then your self-employment turnover and either expenses or the allowance. The short self-employment pages are enough below £85,000 of turnover. The system calculates the bill, which for most employed side hustlers is simply 20 or 40 per cent of the side profit plus any Class 4 National Insurance.
File well before the deadline the first time. First returns hit snags, a missing UTR activation code, a forgotten Government Gateway login, and none of them are fun to discover on 30 January.
Step 5: Deadlines and Paying
- 31 October: paper return deadline (almost nobody should use this).
- 31 January: online filing deadline and payment deadline for the year just declared.
- Payments on account: if your bill tops £1,000 and little of your tax is collected through PAYE, HMRC asks for advances towards the next year in January and July. Budget for this, it surprises almost everyone the first time.
First-time Etsy filer: 40 minutes of her time, £212 bill
Client J runs an Etsy shop selling prints alongside a teaching job: £3,100 of sales, £700 of costs in her first proper year. She sent us her Etsy yearly summary, her P60 and a screenshot of her costs spreadsheet.
We registered her in May, took the £1,000 allowance (bigger than her real costs), filed in June and her bill came to £212, due the following January. Total time from her: about 40 minutes. The January filers she compares notes with did not believe her.
Frequently Asked Questions
When do I need to register for Self Assessment?
By 5 October following the end of the tax year in which your gross trading income passed £1,000. Pass it during 2025/26 (which ended 5 April 2026) and you must register by 5 October 2026, then file and pay by 31 January 2027.
Should I claim the £1,000 allowance or my actual expenses?
Whichever is bigger. If your real costs (stock, postage, packaging, mileage, fees) are under £1,000, the allowance wins and needs no receipts. If your costs are higher, claim them instead, but you cannot do both.
Do I have to do payments on account?
Only if your Self Assessment bill is over £1,000 and less than 80 per cent of your tax is collected at source. Many side hustlers with day jobs stay under this line, but if you cross it, you pay 50 per cent advances towards next year in January and July.
Do I need a separate bank account for my side hustle?
Not legally, but it makes everything easier. A separate account turns your bank statement into a near-complete business record and keeps HMRC questions away from your personal spending.
Want your first return done for you?
At Your Tax Help Accountants in Stanmore, we handle first-time Self Assessment registrations and returns for sellers, drivers, creators and freelancers across the UK. You send the statements, we do the rest. Fixed fee, filed early, refund chased if one is due.
Or email info@yourtaxhelp.co.uk | yourtaxhelp.co.uk
General guidance only. Not personal tax advice. Contact us for advice specific to your situation. All figures are for the 2026/27 tax year unless otherwise stated.