Filing your first self-assessment tax return feels daunting. The forms look complicated, the jargon is confusing, and the penalties for getting it wrong are real.
But here's the truth: for most self-employed people, the process is straightforward once you understand what goes where. This guide walks you through every step, from registration to clicking "submit."
You need to file a self-assessment tax return if any of these apply:
| Date | What happens |
|---|---|
| 6 April | Start of the tax year |
| 5 April (following year) | End of the tax year |
| 5 October | Deadline to register for self-assessment (new filers) |
| 31 October | Paper tax return deadline |
| 31 January | Online tax return + payment deadline |
| 31 July | Second payment on account deadline (if applicable) |
If you haven't already, register as self-employed on the GOV.UK self-assessment page.
You'll need your National Insurance number. HMRC will post you:
Don't leave this to January. If you register late, you may not receive your codes in time to file.
Go to HMRC online services and create an account if you don't have one. You'll need your UTR and activation code to enrol for self-assessment.
Once enrolled, you can view your tax return, submit it, and check your tax position — all online.
Before you start filling in the form, collect:
Self-assessment is based on your profit, not your revenue. The basic formula:
Total Income − Allowable Expenses = Taxable Profit
If you use the cash basis (most sole traders do), you record income when you receive it and expenses when you pay them. Simple.
Log in to HMRC and work through the sections. For a straightforward self-employed return, you'll mainly need:
The online system guides you through each section. You can save and come back to it — you don't have to finish in one sitting.
This is where you save money. Common allowable expenses for self-employed people:
| Category | Examples |
|---|---|
| Office & supplies | Stationery, printer ink, postage |
| Phone & internet | Business proportion of bills |
| Software & tools | Accounting software, design tools, hosting |
| Travel | Business mileage (45p/mile first 10,000), public transport, parking |
| Marketing | Website costs, advertising, business cards |
| Professional fees | Accountant, solicitor, professional body membership |
| Insurance | Professional indemnity, public liability |
| Use of home | Simplified expenses: £10/month (25-50 hrs), £18 (51-100 hrs), £26 (101+ hrs) |
| Training | Courses that update existing skills (not new career training) |
Before you hit submit:
Once submitted, you'll get a confirmation with a reference number. Save this.
Your tax is due by 31 January. Payment options:
HMRC's bank details and your payment reference are shown in your online account.
If you wait until January to register, you won't get your UTR and activation code in time. Register as soon as you start self-employed work.
HMRC can see your bank records if they investigate. Include all self-employed income, even cash payments and small amounts. Omitting income — even accidentally — can trigger penalties.
Many first-timers underclaim because they don't realise what's allowable. If you work from home, use your phone for business, or drive to clients — you likely have expenses to claim.
A good rule of thumb: set aside 25-30% of your profit throughout the year. Open a separate savings account and transfer regularly. Don't spend it.
If your tax bill is over £1,000 (and less than 80% was collected at source), HMRC will ask for payments on account — advance payments towards next year's bill. This catches many people off guard. Read our guide on payment on account →
As self-employed, you pay:
These are calculated automatically when you submit your return. No separate registration needed.
For a straightforward sole trader setup — one income source, simple expenses — you almost certainly don't need one. HMRC's online system is designed for self-filers.
Consider an accountant if:
Many accountants charge £150-£400 for a basic self-employed return. Compare that against your time and confidence level.
HMRC requires you to keep records for at least 5 years after the 31 January submission deadline. That means records for the 2024/25 tax year must be kept until at least 31 January 2031.
What to keep:
From April 2026, self-employed people earning over £50,000 will need to keep digital records and submit quarterly updates to HMRC under Making Tax Digital for Income Tax. This threshold drops to £30,000 from April 2027.
If this applies to you, start using MTD-compatible software now. Check your MTD readiness →
The Getting-Paid Toolkit includes invoice templates, expense tracking sheets, payment chasing sequences, and compliance checklists — everything a new freelancer needs to stay on top of money.
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