Free template · UK 2026/27
Self Assessment Registration Checklist
A free 12-step checklist for UK sole traders registering for Self Assessment for the first time. Fill in the details as you go and they save automatically in your browser. Print, save as a PDF, or share by sending a link.
By Justin Logan · Updated for tax year 2026/27 (6 April 2026 to 5 April 2027)
UK side hustle tax · 2026/27
Self Assessment Registration Checklist
For UK sole traders registering for the first time. Work through it once and keep it for your records.
2026/27 edition
thesecondincome.uk
§ Your details — fill in once, keep for reference
on screen this saves to your browser · in print, write directly on the linesFirst, decide if you need to register
"Gross" means everything that landed in your account before any expenses are taken off. If under £1,000, you do not need to register (covered by the £1,000 trading allowance). Check the Trading Allowance Calculator if you are unsure.
Other triggers force registration too: rental income over £1,000, dividend income over £500, large capital gains, partner of a partnership, High Income Child Benefit Charge. See gov.uk: who must send a tax return.
Gather your information
Format: AB 12 34 56 C. Find on payslip, P60, or HMRC letter. No NI number? Apply at gov.uk/apply-national-insurance-number first. Write yours into the panel above.
10-digit number, e.g. 1234567890. You only have one if you have filed an SA return before. Forgotten yours? Find it at gov.uk/find-utr-number. New to SA? You will get one once you register (step 7). Write yours into the panel above when it arrives.
Not the day you first earned money. The day you started offering your service or product. Backdating much further than a year may raise questions. Write yours into the panel above.
If you have moved within 3 years, previous addresses too. HMRC uses these for identity matching. Write yours into the panel above.
Register online
Pick the "self-employed" path. Free, 10-15 minutes. You will be asked for steps 3-6. Deadline: 5 October 2027 for 2026/27 income.
If you do not have one, you will be prompted. Keep user ID and password somewhere secure, you need them every year. Write your Gateway user ID into the panel above.
HMRC posts your UTR, then sends an activation code separately (1-2 more weeks). Activate within 28 days of receiving the code or it expires.
Set up for next year
2026/27 online return due by 31 January 2028. Tax due same date. Set a reminder for 1 December 2027 to start preparing.
HMRC requires records for at least 5 years after the 31 January filing deadline (so until 31 January 2033 for 2026/27 records). Paper, photos, or accounting software all fine.
Not legally required for sole traders but makes record-keeping dramatically easier. Mixing personal and business funds is the single biggest cause of disorganised SA returns.
Tide — UK-focused, full sole-trader and Ltd Co support, integrates with most UK accounting tools. Open a Tide account →
Revolut Business — international friendly, free expense categorisation, multi-currency. Open Revolut Business →
Key dates · 2026/27
Useful links
→ Register for SA
→ Apply for NI no
→ Find lost UTR
→ Who must file
What next
Side Hustle Tax Calculator
Once you are registered, work out exactly how much Income Tax and Class 4 NI you will owe for 2026/27. Handles dividends, Scottish bands, the trading allowance, and the first-year Payment on Account schedule.
Open calculator › CalculatorTrading Allowance Calculator
Not sure whether you even need to register? Check whether your gross side hustle income is above the £1,000 threshold first.
Open calculator › Read nextDo I need to tell HMRC about my side hustle?
The full plain English explainer of what triggers a Self Assessment registration, in case you want more context before completing the checklist.
Read article › Read nextThe £1,000 Trading Allowance, explained
Full breakdown of how the trading allowance works for 2026/27, who qualifies, and the common mistakes HMRC flags.
Read article ›This template is a guide based on published HMRC rules for the 2026/27 UK tax year. It does not constitute personal tax advice. Your form data stays in your browser only, we never see it. For your specific situation, consult HMRC or a qualified UK accountant.