Self Assessment Tax Return Dates & Deadlines UK

Self Assessment is the HMRC system for individuals to report income and pay tax on sources not covered by PAYE, such as self-employment, rental income, dividends, foreign earnings, or high untaxed income. Sole traders, freelancers, landlords, company directors taking dividends, and others with complex tax affairs must file a Self Assessment tax return annually.

Missing deadlines triggers automatic penalties starting at £100, plus interest on late payments and potential further fines. With Making Tax Digital (MTD) for Income Tax rolling out gradually (starting for some in April 2026), staying on top of dates is more important than ever. This guide covers the main deadlines relevant in 2026, focusing on the current and upcoming tax years.

Understanding the Tax Year

The UK tax year runs from 6 April to 5 April the following year.

• 2024/25 tax year: 6 April 2024 – 5 April 2025 (Most recent return deadlines passed in 2026: online filing and payment by 31 January 2026.)
• 2025/26 tax year: 6 April 2025 – 5 April 2026 (Current year ending soon; returns due in 2026/27.)

Deadlines are fixed for the previous tax year’s return. For example, the return for income earned in 2025/26 must be filed by deadlines in late 2026 and early 2027.

Key Self Assessment Deadlines

Here are the core dates every Self Assessment taxpayer should mark:

1. 5 October — Deadline to notify HMRC of chargeability / register for Self Assessment If you need to file a return for the previous tax year (e.g., started self-employment or earned untaxed income >£1,000 in 2025/26), tell HMRC by 5 October 2026.
   • Use form SA1 (non-self-employed) or CWF1 (self-employed).
   • Late registration can lead to penalties, though HMRC may extend filing time.
   • If you register late, HMRC sends a notice with a new 3-month filing deadline from the notice date.
2. 31 October — Paper tax return deadline For the previous tax year (e.g., 2025/26), HMRC must receive your paper SA100 form by 31 October 2026.
   • Few use paper now; missing this forces online filing.
   • Late paper returns still attract penalties.
3. 31 January — Online tax return and payment deadline Submit your online Self Assessment return by 11:59pm on 31 January 2027 for the 2025/26 tax year.
   • This is the most common deadline.
   • Pay any tax owed (balancing payment) by the same date to avoid interest and penalties.
   • If you want HMRC to collect tax via your PAYE code (if employed), submit by 30 December (earlier deadline).
   • For 2024/25, this deadline was 31 January 2026 (recently passed; late filers face £100+ penalties).
4. 31 July — Second payment on account If you paid tax via payments on account last year (common for self-employed with liability >£1,000), pay the second half by 31 July (e.g., 31 July 2026 for 2024/25 balancing).
   • Payments on account: 31 January (first) and 31 July (second), each 50% of previous year’s liability (adjusted if over/under).

Additional Important Dates in 2026

• 6 April 2026 — Start of 2026/27 tax year; online filing opens for 2025/26 returns (usually early April).
• 31 July 2026 — Payment on account deadline for 2025/26 (first payment).
• MTD for Income Tax phased rollout: From April 2026, some higher earners (self-employment/property income >£50,000) start quarterly digital updates. Full rollout follows; check HMRC for eligibility.

Penalties for Missing Deadlines

HMRC enforces strictly:

• Late filing — Automatic £100 (even if no tax due), then daily £10 (up to 90 days), 5% of tax due at 6/12 months, plus more.
• Late payment — Interest from 31 January + late payment penalties (5% at 30 days/6 months/12 months).
• Reasonable excuses (e.g., serious illness) may reduce penalties—contact HMRC promptly.

Tips for Staying Compliant

• Register early if new to Self Assessment.
• Use HMRC’s online portal (Government Gateway) for filing—faster and gives extra time vs paper.
• Keep digital records (especially with MTD approaching).
• Estimate tax liability mid-year to budget for January payments.
• For non-UK residents (like those in Delhi managing UK income), deadlines remain the same; use online filing and check double taxation treaties.
• Get help from an accountant if complex (e.g., dividends, foreign income).

Why Deadlines Matter

Hitting these dates avoids penalties, interest, and stress. Many miss the 31 January deadline each year—HMRC reported

around 1 million late in recent years. File early (from April) when records are fresh.

Whether you're a sole trader, freelancer, landlord, or director extracting dividends, Self Assessment ensures correct tax on untaxed income. Mark your calendar, set reminders, and file on time—your future self (and wallet) will thank you.

Disclaimer: The information provided in this article is for general informational and research purposes only. Company details, features, services, and market positions may change over time. Readers are advised to visit official company websites and conduct independent research before making any business decisions or purchasing services.