Self-Assessment Tax Estimator

Q: Who needs to file a self-assessment tax return?

You must file a self-assessment return if you are self-employed, a company director, have income over £100,000, have untaxed income over £2,500, or if HMRC asks you to. The deadline for online returns is 31 January following the end of the tax year.

Q: What is the self-assessment deadline?

The deadline for filing your online self-assessment return is 31 January following the end of the tax year. For 2025/26 (tax year ending 5 April 2026), the deadline is 31 January 2027. Paper returns must be filed by 31 October.

Q: How much tax do I pay on self-employment income?

Self-employed individuals pay income tax on profits above the personal allowance (£12,570 in 2026/27) at 20%, 40% or 45%. They also pay Class 4 National Insurance at 9% on profits between £12,570 and £50,270, and 2% above that.

Q: What is a payment on account?

Payments on account are advance payments towards your next tax bill. HMRC requires two payments per year — 31 January and 31 July — each equal to 50% of your previous year's tax bill. First-time filers pay their full bill plus the first payment on account in January.

Q: Can I reduce my tax bill through expenses?

Yes. Allowable business expenses reduce your taxable profit. Common deductible expenses include office costs, travel, equipment, professional fees and marketing. Personal expenses are not deductible. If you work from home you may be able to claim a proportion of household costs.

Estimate your income tax and National Insurance for 2026/27. Enter your income and deductions — no signup required.

Using 2026/27 figures

This tool estimates income tax, employee National Insurance and (if selected) student loan repayments from the figures you enter, including personal pension (relief at source) and Gift Aid effects on your basic rate band. It does not cover every scenario — for example Scottish income tax, other income sources, or complex PAYE adjustments. Illustrative payments on account are shown when you owe additional tax. Always verify your tax position with HMRC or a qualified accountant before filing.

Income

Employment income (gross salary) (£) Your gross salary before tax and NI — from your P60 or payslip

Tax already deducted via PAYE (£) Income tax already paid through your employer — shown on your P60

NI already deducted via PAYE (£) National Insurance already paid through your employer — shown on P60

Deductions

Personal pension contributions (£) Annual contributions to a personal pension (not workplace pension deducted from salary). Reduces your taxable income.

Gift Aid donations (£) Total Gift Aid donations made in the tax year. Extends your basic rate band.

Student loan

Student loan plan

Enter your employment income above to see your estimated tax position.

Key self-assessment dates

Tax year — runs from 6 April to 5 April (e.g. 2026/27 ends 5 April 2027).

Online return — must be filed by midnight 31 January after the tax year ends.

Balancing payment — any tax owed for the year is usually due 31 January after the tax year end.

Payments on account — two instalments (January and July) based on the previous year's bill, unless your liability is small or you've reduced them with a claim.

Paper returns — earlier deadline (31 October) if not filing online.

What counts as allowable expenses?

Common self-employed deductions include: office costs, stationery, phone and internet (business proportion), travel for business, equipment, stock, professional and accountancy fees, marketing, and bank charges. Costs must be wholly and exclusively for the business.

Typically not allowed: personal spending, commuting to your usual workplace, clothes (unless specialist protective or uniform), client entertainment.

If you use something for both business and personal use, you usually claim only the business share. If in doubt, check HMRC’s guidance or speak to an accountant.

Common questions

Who needs to file a self-assessment tax return?

You must file if you are self-employed, a company director, have income over £100,000, have untaxed income over £2,500, or if HMRC asks you to. The online deadline is 31 January following the end of the tax year.

What is the self-assessment deadline?

Online returns are due by 31 January after the tax year ends — for example, 2025/26 (ending 5 April 2026) must be filed by 31 January 2027. Paper returns are due by the previous 31 October.

How much tax do I pay on self-employment income?

Self-employed profits above the personal allowance are taxed at 20%, 40% or 45%. Class 4 NI uses the thresholds and rates for the selected tax year in this site’s HMRC config.

What is a payment on account?

Advance payments towards next year’s bill — usually two instalments in January and July, each half of the previous year’s liability (with exceptions for first-time filers and small liabilities).

Can I reduce my tax bill through expenses?

Yes — allowable business expenses reduce taxable profit. Common examples include office costs, travel, equipment and professional fees. Personal costs are not deductible.

This calculator provides estimates only. Self-assessment tax returns are complex and your circumstances may vary. Always verify your figures with HMRC or a qualified accountant before filing. Filing an incorrect return can result in penalties.

Want someone to file for you?

TaxScouts offers fixed-fee self-assessment filing from £169 — a qualified accountant files your return for you.

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✓ No signup required ✓ No data sent to any server ✓ Updated for 2026/27