UK self-assessment is genuinely not that hard. But HMRC has done a terrible job of explaining it.
Here's the plain English version for freelancers.
What self-assessment actually is
It's just a tax return. You tell HMRC:
- What you earned (from all sources)
- What your allowable business expenses were
- HMRC calculates what you owe
That's it. Once a year. Deadline: 31 January.
Who has to do it
If you're self-employed (sole trader or freelance) and earned more than £1,000 from self-employment in a tax year, you must register and file.
You also need it if:
- You earn over £100,000 total
- You have rental income over £2,500
- You have untaxed income (dividends, savings interest above your allowance)
The timeline
April 6: New tax year starts
July 5: Deadline to register as self-employed if you started working for yourself in the previous year
October 31: Deadline for paper returns (nobody uses this)
January 31: Online return deadline AND payment deadline
Here's what catches people out: you pay two things on January 31.
- The tax you owe for the year just gone
- A "payment on account" — 50% of this year's tax, as an advance payment for next year
So if you owe £2,000, you actually pay £3,000 on January 31. First year is brutal.
The expenses that matter most
HMRC allows you to deduct "wholly and exclusively" business expenses. The ones freelancers miss:
- Home office: either flat rate (£6/week) or % of home costs
- Phone bill: % used for business
- Professional subscriptions: software, tools, memberships
- Training and courses: must be related to your existing trade
- Travel: mileage at 45p/mile for first 10,000 miles
- Accountant fees: yes, you can deduct the cost of doing your taxes
Making Tax Digital — this is changing soon
If your income is over £50,000, you'll need to use MTD for Income Tax from April 2026. That means quarterly digital submissions instead of one annual return.
Free readiness checker: landolio.com/tools/mtd-readiness-checker
If you want the full MTD preparation checklist + template spreadsheet: MTD Readiness Toolkit — £14, use LAUNCH50 for 50% off.
The honest truth about accountants
For a simple sole trader return, you don't need one. HMRC's own software handles it fine.
But if you:
- Have employees
- Have property income
- Are considering incorporating
- Earn over £50k
...the accountant pays for itself.
What I got wrong in my first year
Didn't keep receipts. Couldn't claim half the expenses I should have. Lost maybe £400.
Now I take a photo of every receipt the moment I get it. Two seconds. Saves hours later.
Any questions about specific situations? Drop them below — happy to help.
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