Year-one timeline
The first Self Assessment return is where most freelancers make expensive mistakes — usually because they didn't know a specific relief or thought they could file 'later'. This guide walks the first-time filer through the sequence from registration through to submission, focused on the decisions that only matter in year one.
Year-one timeline
Month 1-3 of freelancing: set up basic bookkeeping. Track income and expenses from day one.
By 5 October (of the tax year you started): register for Self Assessment.
Wait 10-14 days: receive UTR by post.
Set up Government Gateway and activate SA online services.
By 31 January (following the tax year end): file the return and pay any tax owed.
If you started freelancing 15 May 2025, first return covers 15 May 2025 → 5 April 2026, filed by 31 January 2027.
The reliefs first-time filers miss most
Higher-rate pension relief. Personal pension contributions get basic-rate automatically; higher-rate relief must be claimed on SA. Value: 20% of contribution amount. Missed frequently.
Marriage Allowance. If you're basic-rate and spouse earns below personal allowance, spouse can transfer £1,260 of allowance to you. £252 tax saving per year.
Trading allowance. First £1,000 of self-employment income can be exempt if that's better than claiming actual expenses.
Class 2 NI voluntary contributions. Even if profits under £6,725, paying voluntary Class 2 protects state pension entitlement.
Business use of home — flat rate £312/year is easy to claim; many miss it because they don't have a dedicated office.
First-time filing mistakes and how to avoid them
Missing the £1,000 payments on account trigger. If tax owed > £1,000, HMRC requires 50% of the bill as advance for the following year. Budget accordingly.
Claiming personal expenses. Coffee shop meetings, personal phone bills, general clothing — these get flagged in HMRC enquiries.
Wrong year's income. Include income earned in the tax year (6 April to 5 April), not the calendar year.
Filing without a UTR. Register early; without a UTR you can't submit.
Ignoring reasonable-excuse deadlines. If you'll miss 31 January, request Time to Pay or reasonable excuse BEFORE the deadline, not after.
Worked example
Alex's first year of freelancing: 20 July 2024 → 5 April 2025 (about 8.5 months). Income: £27,000. Expenses: £3,100. Home office flat rate: £312. Net profit: £23,588. Timeline: registered 3 September 2024, UTR arrived 12 September, activated Government Gateway 15 September. Filed on 6 December 2025. HMRC calculation: £23,588 - £12,570 personal allowance = £11,018 taxable. Income tax: £11,018 × 20% = £2,204. Class 4 NI: £11,018 × 6% = £661. Total: £2,865. Under £1,000... no wait, £2,865 > £1,000 → payments on account do apply. First POA: £1,432 due 31 January 2026 alongside the £2,865 balancing. Total 31 January 2026: £4,297.
Reference table
| Milestone | Deadline | Consequence of missing |
|---|---|---|
| Register for SA | 5 Oct (year of starting) | Failure to Notify penalty |
| Receive UTR | 10-14 days after registering | Can't file without it |
| Set up Government Gateway | Same as UTR | Can't file online |
| File first return | 31 Jan following tax year | £100 late-filing penalty |
| Pay first balancing tax | 31 Jan | 5% surcharge at 30 days late |
| Pay first POA | 31 Jan (same day) | Same penalty ladder |
First-time filer checklist
- Register for Self Assessment before 5 October
- Set up basic bookkeeping — accounting software or spreadsheet from day 1
- Separate business bank account (not required for sole traders, but keeps records clean)
- Keep every receipt (paper or digital)
- Record income and expenses monthly, not annually
- Note the £1,000 payment-on-account threshold when modelling first bill
- Start a tax savings account with 25-30% of each invoice
- Consider using an accountant for the first year to learn the ropes
Yes — many freelancers do. A first-year accountant fee of £300-£500 often surfaces reliefs and structures worth much more. Consider learning to file yourself in year two.
HMRC recalculates after you file the return, showing you the correct amount. Pay the difference immediately to avoid late-payment surcharges.
You'll get a refund after filing. HMRC pays it directly to a specified bank account or by cheque.
No. Self Assessment registration is not reported to credit reference agencies.
You still file Self Assessment for that tax year. You then formally deregister so HMRC doesn't expect further returns. Deregistration is via your online account or phone.
Sources & official references
Related on FreelanceToolkit UK
This guide is general information based on UK rules for the 2025/26 tax year. It is not personal tax or legal advice. For decisions affecting your tax position or legal exposure, consult a qualified accountant or solicitor.