📝 Self Assessment Calculator

2026/27 · Trading profit · Rental income · Class 4 NI

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Reduces your taxable income

Self Assessment Estimate — 2026/27

Net Profit (trading)—
Total Income—
Personal Allowance£12,570
Income Tax—
Class 4 NI (self-employed)—
Total Tax Bill—
⚠️ Class 2 NI (£3.45/week if profits above £12,570) may also apply. Payments on account may be required. Always verify with a qualified accountant.

Who Needs to File a Self Assessment Return?

You must complete a Self Assessment tax return if you are self-employed (sole trader or partner), a company director, have income over £100,000, have untaxed income over £2,500, are a higher-rate taxpayer with savings or investment income, or receive rental income above the £1,000 property allowance.

Key Deadlines 2026/27

  • 5 October 2025 — register for Self Assessment if new to it
  • 31 October 2025 — paper return deadline
  • 31 January 2026 — online return and payment deadline
  • 31 July 2026 — second payment on account

Class 4 National Insurance for the Self-Employed

Self-employed people pay Class 4 NI on profits above £12,570 at 6% (reduced from 9% in April 2024), and 2% on profits above £50,270. Class 2 NI (a flat rate of £3.45/week) is also due if profits exceed £12,570.

⚠️ Payments on account: if your tax bill exceeds £1,000, HMRC requires you to make two advance payments toward next year's bill (each 50% of the current year's liability), due 31 January and 31 July.