Self Assessment Calculator
Estimate your self-employment tax bill for 2026/27
Last updated: August 2026 · 2026/27 tax rates
Self-Employed Income
Total business income
Business costs you can deduct
Other Income
Employment, rental, etc.
From shares or company
Deductions
Personal pension payments
Charitable donations
Different income tax bands
Total Tax Bill 2026/27
£7,132
Income Tax + National Insurance
Effective Rate
17.8%
Tax Breakdown
Income Tax Calculation
National Insurance Calculation
Payment Schedule
You pay your tax bill in three installments: a balancing payment plus two payments on account for next year.
31 January 2028
Balancing payment + 1st payment on account
£10,698
• Balancing payment: £7,132
• 1st payment on account: £3,566
31 July 2028
2nd payment on account
£3,566
Total to pay in 12 months: £14,264
Self Assessment Guide
You Must File Self Assessment If You:
- • Are self-employed (sole trader or partnership)
- • Have untaxed income over £1,000 (excluding employment)
- • Are a company director (unless PAYE covers all tax)
- • Have income over £100,000
- • Receive income from abroad
- • Rental income over £2,500 (or £1,000 with expenses)
- • Capital gains above the annual allowance
- • Want to claim certain tax reliefs
Registration & Filing
- • 5 October: Register if new to Self Assessment
- • 31 October: Paper return deadline
- • 31 December: File online to see calculation before Jan
- • 31 January: Online filing & payment deadline
Late Filing Penalties
- • 1 day late: £100 penalty
- • 3 months: £10/day (max £900)
- • 6 months: £300 or 5% of tax
- • 12 months: £300 or 5% of tax again
Tax year 2026/27 (6 April 2026 - 5 April 2027) | Rates and allowances subject to change
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Reviewed by
Alexandre Bernier, LLM (UK), CFP®, CIM®, PFP®. Financial planner with 18 years in banking and wealth management, holding a UK master of laws and the Canadian CFP®, CIM® and PFP® designations. Writes and reviews every calculator and article on FinanceToolz.
Last updated: August 2026. How figures are sourced, reviewed and corrected is set out in our editorial policy. This is general information, not regulated financial advice.
Sources
Every rate and threshold used by this calculator is taken from the official pages below. If a figure here disagrees with one of these, the official page is right, please tell us.