Self Assessment Calculator – Estimate Your 2025/26 Tax Bill
Running a business or earning income outside of PAYE? Our free Self Assessment Calculator makes it easy to estimate how much income tax and National Insurance you may owe for the 2025/26 tax year.
Simply enter your employment income, self-employment profits, and dividends, and our calculator will give you an instant breakdown of:
Income Tax on your earnings and self-employment income
Dividend Tax (including your £500 allowance)
National Insurance contributions (Class 1 and Class 4)
Your total estimated Self Assessment tax bill
This tool works for both England, Wales, Northern Ireland, and Scotland, using the latest tax bands and rates for the 2025/26 financial year.
Self Assessment Calculator
| Breakdown | Amount |
|---|---|
| Income Tax on earnings & self‑employment | £0 |
| Dividend Tax | £0 |
| NIC – Employee (Class 1) | £0 |
| NIC – Self‑employed (Class 4) | £0 |
| Personal Allowance used | £0 |
| Dividend allowance used | £0 |
| Total estimated bill | £0 |
This is a guide only and not tax advice. Actual liabilities depend on your full circumstances. For complex cases (student loans, child benefit charge, benefits-in-kind, marriage allowance, ISA interest, etc.) please speak to an accountant.
What is a Self Assessment Calculator
A Self Assessment Calculator helps you estimate how much tax you owe when you submit your annual Self Assessment tax return to HMRC. It’s especially useful if you:
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Run a small business or work as a sole trader
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Receive dividends from your company
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Have a mix of employment and self-employment income
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Want to plan ahead for your January and July payments on account
Instead of waiting until you file your return, you can use this calculator to budget for your upcoming tax payments.
How to Use The Calculator
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Enter your income – add your total earnings from employment, self-employment profits, and any dividends received.
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Choose your region – select England/Wales/NI or Scotland, as the tax bands differ.
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Click Calculate – get an instant estimate of your total income tax, National Insurance, and dividend tax for the 2025/26 tax year.
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Review your breakdown – see exactly how your personal allowance and allowances are used.
The calculator updates automatically to give you a clear and simple estimate of what you owe under the UK’s Self Assessment system.
Why Use Grow My Acorns Self Assessment Calculator?
Our calculator is built specifically for UK freelancers, contractors, and small business owners who need a quick, accurate tax estimate.
✅ Uses 2025/26 HMRC rates and thresholds
✅ Covers employment income, self-employment, and dividends
✅ Works for both UK and Scottish taxpayers
✅ Includes NIC Class 1 & 4 calculations
✅ No registration or download required – instant results online
Next Steps After Using the Self Assessment Calculator
Once you’ve estimated your tax:
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Plan your HMRC payments on account (if applicable).
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Set aside funds monthly to avoid surprises in January.
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Review ways to reduce your tax liability, such as pension contributions or claiming business expenses.
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Explore our other free tools, including:
This Self Assessment Calculator is designed for general guidance and estimation purposes only. It does not replace professional financial or tax advice. For personalised support or complex tax situations (e.g., student loans, pension contributions, child benefit charge, or multiple income streams), always consult a qualified accountant.