Self Assessment Tax Calculator
The AbraTax Self Assessment tax calculator provides an estimate of Income Tax and National Insurance for the selected tax year using the supported income sources entered. It does not determine the amount HMRC will assess.
Who This Calculator Is For
This calculator is designed for anyone who completes a Self Assessment tax return, including:
- Sole traders and freelancers earning income from self-employment
- Landlords receiving rental income
- Employees or individuals with supported income that may not be fully taxed through PAYE
- Company directors receiving dividends or salary outside PAYE
- People with savings interest or dividends; this calculator does not model foreign income or capital gains
What You Need to Know
Income Tax Bands and Tax Years
For 2025/26 and 2026/27, the standard Personal Allowance is £12,570. The following bands apply to England, Wales, and Northern Ireland; earlier supported years differ and Scottish non-savings rates are different:
- Basic rate: 20% on income between £12,571 and £50,270
- Higher rate: 40% on income between £50,271 and £125,140
- Additional rate: 45% on income above £125,140
If your income exceeds £100,000, your Personal Allowance is reduced by £1 for every £2 you earn over that threshold. This creates an effective 60% Income Tax rate on income between £100,000 and £125,140.
National Insurance for the Self-Employed
If you are self-employed, you may pay Class 4 National Insurance on your profits. For 2025/26 and 2026/27 the rates are:
- 6% on profits between £12,570 and £50,270
- 2% on profits above £50,270
You may also choose to pay Class 2 National Insurance voluntarily if your profits fall below the Small Profits Threshold, which protects your entitlement to the State Pension and certain benefits.
Payments on Account
HMRC generally requires two payments on account unless the previous Self Assessment bill was less than £1,000 or more than 80% of the tax was paid outside Self Assessment. The payments are normally due on 31 January and 31 July. This calculator shows an estimate under its stated assumptions; the HMRC statement or online account confirms whether payments are required and the amounts due.
How to Use the Self Assessment Tax Calculator
- Select the tax year and where you live.
- Enter your self-employment and property profits after allowable expenses.
- Include employment income, tax already paid, dividends, and untaxed savings interest where applicable.
- The calculator will show your estimated Income Tax and National Insurance liability.
- The result shows a payments-on-account estimate when the modelled conditions apply.
Frequently Asked Questions
What is Self Assessment?
Self Assessment is HMRC's system for collecting Income Tax that has not been deducted at source through PAYE. Registration depends on the type and amount of income and the person's circumstances; this calculator does not determine whether registration or a return is required.
When is the Self Assessment deadline?
The online filing deadline is 31 January following the end of the tax year. Paper returns must be filed by 31 October. The 31 January deadline also covers any tax owed for the previous year and the first payment on account for the current year.
What counts as allowable expenses?
Allowable expenses are costs you incur wholly and exclusively for your business. Common examples include office costs, travel, equipment, professional fees, and marketing. Personal costs and those with a dual personal and business purpose are generally not allowable, or only partly so.
How accurate is the estimate?
The calculator provides an estimate based on the figures you enter and the tax rates and bands for the selected year. Your actual liability may vary depending on reliefs, deductions, or adjustments that HMRC applies when processing your return.
Do I need to register for Self Assessment even if I do not owe tax?
If HMRC has sent a notice to file, a return must be submitted unless HMRC withdraws the notice. Otherwise, registration depends on the type and amount of income and the person's circumstances. HMRC's checker provides the current criteria.
Limits of This Illustration
The result displays a modelled January total and, where applicable, a second payment on account. It is not a recommendation about how much money to reserve.
Business and self-employment records normally need to be kept for at least five years after the 31 January filing deadline. For an on-time return without business income, the normal period is at least 22 months after the end of the tax year. Longer periods can apply in some circumstances.
Where the calculator's assumptions do not match the facts, HMRC or an appropriately qualified professional can explain the rules that apply to the specific circumstances.
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