Overview

• The cut-off to register for 2024–25 Self Assessment is 5 October 2025, and missing it triggers an automatic £100 penalty with further fines and interest if not resolved.
• Those who must register include new self-employed workers, landlords, some company directors, and anyone with more than £1,000 of untaxed income from side hustles or online trading.
• Returns for the 2024–25 tax year can still be filed online by 31 January 2026, but failing to register now can delay refunds and create complications if HMRC makes contact.
• At roughly 5% interest, the Personal Savings Allowance is quickly exhausted—around £19,600 in savings for basic-rate and £9,800 for higher-rate taxpayers—bringing more savers into tax for the first time.
• Analysts estimate 2.64 million people will owe tax on savings interest in 2025/26 with the Treasury taking over £6 billion, and HMRC can impose 30%–100% penalties for deliberate evasion or adjust tax codes that reduce take-home pay.