Filing taxes as a self-employed individual in the UK doesn’t have to be overwhelming. Whether you’re a freelancer, sole trader, or business partner, understanding your Self Assessment obligations for the 2024/25 tax year will help you stay compliant and avoid costly mistakes.
This straightforward guide covers everything you need to know: eligibility requirements, critical submission dates, what information to gather, and practical tips to make the process smoother.
Understanding Your Self Assessment Obligation
When you work for yourself, your primary tax responsibility isn’t about producing company reports—it’s completing your Self Assessment tax return. This annual submission tells HMRC about your earnings, deductible costs, and calculates what you owe in Income Tax and National Insurance.
The main form (SA100) serves as your foundation, with additional pages added depending on your situation. Sole traders complete the SA103 supplement, while those in partnerships use SA104. Think of this combined submission as your official financial snapshot for the year.
Do You Need to Submit a Return?
Self Assessment isn’t universal—HMRC only requires it in specific circumstances. You’ll need to file if you:
- Earned more than £1,000 from self-employment during the tax year
- Work as a partner in any business partnership
- Collect rental income that isn’t taxed through regular employment deductions
- Receive substantial untaxed earnings from investments, dividends, or foreign sources
- Serve as a company director (with rare exceptions)
- Have total income exceeding £150,000
- Must pay the High Income Child Benefit Charge
Some people voluntarily file even with lower earnings—perhaps to claim valuable tax reliefs, demonstrate income for mortgage applications, or secure National Insurance credits toward their state pension. If you’re uncertain about your situation, HMRC’s online checking tool provides personalized guidance.
Mark These Critical Dates
Timing matters enormously when it comes to Self Assessment. For the 2024/25 tax year (covering 6 April 2024 through 5 April 2025), these deadlines are non-negotiable:
5 October 2025 – Last day to register if you’re new to Self Assessment
31 October 2025 – Paper return submission deadline
31 January 2026 – Online filing deadline and payment due date for any outstanding tax
Online submission has become the standard choice for good reason: it gives you three extra months compared to paper forms, automatically handles calculations, and processes faster. The digital approach has become so dominant that paper returns now represent a tiny fraction of total submissions.
What Information Goes Into Your Return
Your Self Assessment captures all taxable income, extending well beyond just freelance earnings. You’ll typically need to report:
- Business income and legitimate expense deductions
- Your share of partnership profits
- Property rental income from domestic or international sources
- Dividend payments from companies
- Interest earned on savings and investments
- Capital gains from asset sales like shares or additional properties
- Any other income that hasn’t been taxed at source
Start collecting documentation early. HMRC requires you to retain supporting evidence—invoices, receipts, bank records, digital bookkeeping files, and mileage documentation—for five full years after the submission deadline.
Modern cloud accounting tools have transformed record-keeping for many self-employed professionals. These platforms connect to bank accounts, capture receipt images instantly, and prepare data for the upcoming Making Tax Digital requirements launching in April 2026 for qualifying landlords and sole traders.
Filing Methods: Digital vs Traditional
You have two main routes for submission:
Digital Filing: Log into your Government Gateway account and navigate through structured questions about income and expenses. The system performs all calculations automatically and lets you save progress. Many people prefer compatible commercial software over HMRC’s portal for handling complex situations with multiple revenue streams.
Paper Filing: Traditional form SA100 with relevant supplements remains available but comes with drawbacks. The October deadline is significantly earlier, manual calculations increase error risk, and processing takes longer.
Unless you have compelling reasons otherwise, digital filing offers clear advantages for most self-employed taxpayers.
Recent Tax Year Basis Changes
The 2024/25 tax year operates under “tax year basis” rules for reporting business profits. Previously, you could use accounting periods that didn’t align with the tax year and apply adjustments.
Now, profits must match the actual tax year dates (6 April to 5 April). While this simplifies long-term reporting, businesses using different accounting year-ends may have experienced transitional adjustments in 2023/24. Review how these changes affect your current liability and explore available reliefs.
Calculating What You Owe
HMRC determines your tax bill using several factors:
- Taxable profits after allowable expense deductions
- Personal Allowance (£12,570 tax-free for most people)
- Applicable Income Tax rates based on earnings bands
- Class 2 and Class 4 National Insurance for self-employment
- Additional charges if applicable
- Penalties and interest for late submissions or payments
Payments on account often catch people off guard—these are advance payments toward next year’s tax, due on 31 January and 31 July. They’re based on your previous year’s bill, though you can request reductions if circumstances change significantly.
Avoiding Penalties
Late filing triggers automatic consequences. Filing just one day late typically incurs a £100 penalty immediately. After three months, daily charges can apply. Six and twelve months late bring additional penalties and mounting interest charges.
HMRC may waive penalties for genuine “reasonable excuses” with proper documentation, but prevention beats explanation. Filing early—even if you can’t pay immediately—lets you plan ahead.
Common Pitfalls to Avoid
Frequent mistakes include overlooking small income sources like marketplace sales or freelance projects, claiming personal expenses as business costs, mixing personal and business finances, forgetting about payments on account, and ignoring HMRC correspondence.
Remember: expenses must be “wholly and exclusively” for business use to qualify as deductions. When situations get ambiguous, professional guidance prevents expensive errors.
Final Thoughts
Your Self Assessment return represents more than a compliance exercise—it’s a clear picture of your business performance and tax position. Start gathering records now, calendar the key deadlines, and decide whether DIY filing or professional support suits your situation best.
With proper planning and organization, your 2025 tax return becomes a manageable routine task rather than a frantic race against the clock.
