Self Assessment Tax Calculator 2025/26
Work out your UK tax return bill for 2025/26: income tax, Class 4 National Insurance, student loan, payments on account and the total to pay by 31 January 2027.
Return and payment due 31 January 2027
Self-employment (2025/26)
Turnover minus allowable expenses (SA103 net profit). Enter 0 for a loss.
Other income
Gross pay before tax
Tax deducted on your P60
Rent minus allowable costs, or minus the £1,000 property allowance
Bank and building society interest (not ISAs)
From shares or your own limited company (not ISAs)
Reliefs and deductions
Relief at source: what you paid. Your provider adds 25% on top; the gross amount extends your basic-rate band.
Grossed up by 25% and added to your basic-rate band
Only if your income is over £60,000 (High Income Child Benefit Charge)
Paid 31 Jan 2026 and 31 Jul 2026; 0 if this is your first return
Student loan
| 2025/26 Self Assessment | Amount |
|---|---|
| Self-employment profit | £45,000.00 |
| Total income | £45,000.00 |
| Personal allowance | − £12,570.00 |
| Income tax | £6,486.00 |
| Class 4 National Insurance | £1,945.80 |
| Total 2025/26 bill | £8,431.80 |
| Balancing payment | £8,431.80 |
| 1st payment on account for 2026/27 | £4,215.90 |
| Total to pay by 31 January 2027 | £12,647.70 |
| 2nd payment on account, due 31 July 2027 | £4,215.90 |
Income tax, band by band
| Band | Rate | Income | Tax |
|---|---|---|---|
| Personal allowance | 0% | £12,570 | £0.00 |
| Basic rate | 20% | £32,430 | £6,486.00 |
| Income tax | £45,000 | £6,486.00 | |
- Personal allowance = £12,570 = £12,570. It is used against earnings first, then savings, then dividends.
- Income tax = 20% / 40% / 45% on taxable income.
- Class 4 NI = 6% × £32,430.00 = £1,945.80. Class 2: treated as paid (profit at or above £6,845), so £0.
- Payments on account = (income tax + Class 4 − PAYE tax) ÷ 2 = £8,431.80 ÷ 2 = £4,215.90 each.
- Balancing payment = total bill £8,431.80 = £8,431.80.
How much to set aside each month
Paying £12,648 three months late would cost about £877.43 (5% penalty at 30 days plus roughly 3 months of interest at 7.75%, HMRC rate). If you can't pay in full, set up a Time to Pay plan before the deadline.
What if I pay more into a pension?
Total going into the pension; you pay 80%, the provider adds 20%
Paying £800.00 into a personal pension puts £1,000.00 in your pot (the provider claims £200.00 from HMRC). As a basic-rate taxpayer that 20% top-up is all the relief you get, so your Self Assessment bill doesn't change. Higher-rate taxpayers save a further 20% through this return. For 2025/26 the contribution must have been paid by 5 April 2026.
2025/26 deadlines and penalties
- 5 April 2026End of the 2025/26 tax year.
- 5 October 2026Deadline to register for Self Assessment if you're filing for the first time.
- 31 October 2026Paper tax return deadline.
- 30 December 2026File online by now if you want a bill under £3,000 collected through your PAYE tax code (employees only).
- 31 January 2027Online filing deadline. Pay the 2025/26 balancing payment plus the first payment on account for 2026/27.
- Early March 2027Tax still unpaid 30 days after 31 January: 5% late payment penalty.
- 1 May 2027Return 3 months late: £10 a day for up to 90 days (max £900), on top of the £100 penalty.
- 31 July 2027Second payment on account due. Return 6 months late: further £300 or 5% of the tax due. Tax unpaid for 6 months: another 5%.
- 31 January 2028Return 12 months late: another £300 or 5%. Tax unpaid for 12 months: another 5%.
Late filing: £100 immediately, even if no tax is owed. Late payment: 5% of unpaid tax at 30 days, 6 months and 12 months, plus interest at Bank of England base rate + 4% (7.75% since 9 January 2026).
- →Keep records of every allowable expense: phone, software, mileage at 45p a mile, and a share of home costs if you work from home.
- →Use the £1,000 trading allowance only when your real expenses are lower than £1,000.
- →Higher-rate taxpayers: claim the extra relief on personal pension and Gift Aid payments on this return; it isn't automatic.
- →If your profits have fallen, apply to reduce your payments on account (form SA303), but don't go too low or HMRC charges interest.
- →Owe less than £3,000 and have a PAYE job? File online by 30 December to have it collected through your tax code instead.
Sources (gov.uk): personal allowance, UK and Scottish bands and dividend rates for 2025/26 and 2026/27: Income Tax rates and allowances. Class 4 (6% / 2%, £12,570–£50,270) and Class 2 Small Profits Threshold and voluntary rate: NI rates and allowances. Personal Savings Allowance and starting rate, trading allowance, Child Benefit charge, student loan thresholds (2025/26: Plan 1 £26,065, Plan 2 £28,470, Plan 4 £32,745; 2026/27: £26,900, £29,385, £33,795, Plan 5 £25,000), payments on account, penalties and late payment interest.
This tool is for informational purposes only. Always verify results with a qualified professional.
What is the Self Assessment Tax Calculator 2025/26?
This Self Assessment tax calculator works out what you owe HMRC on your 2025/26 tax return, the one that must be filed online and paid by 31 January 2027. Enter your self-employment profit (or your turnover and allowable expenses, or the £1,000 trading allowance), any salary and the tax already taken through PAYE, rental profit, savings interest, dividends, pension contributions and Gift Aid. It calculates income tax band by band, Class 4 National Insurance, any student loan repayment and the High Income Child Benefit Charge, then subtracts what you have already paid to show your balancing payment, your payments on account for 2026/27, and the single figure most people search for: the total to pay on 31 January 2027.
The 2025/26 figures come from HMRC's rates and allowances pages on gov.uk. The personal allowance is £12,570, reduced by £1 for every £2 of adjusted net income above £100,000. In England, Wales and Northern Ireland the basic rate of 20% applies to the first £37,700 of taxable income, 40% up to £125,140 and 45% above. Scottish taxpayers pay 19%, 20%, 21%, 42%, 45% and 48% on their earnings, but UK rates on savings and dividends. Class 4 National Insurance is 6% on profits between £12,570 and £50,270 and 2% above. Class 2 is no longer charged: since 6 April 2024 anyone with profits of £6,845 or more (2025/26) is treated as having paid it, and people below that can pay £3.50 a week voluntarily to protect their State Pension. Dividends above the £500 allowance are taxed at 8.75%, 33.75% and 39.35% in 2025/26, rising to 10.75% and 35.75% for basic and higher-rate taxpayers in 2026/27.
Worked example: a sole trader in England with £45,000 profit for 2025/26 and no other income. Taxable income is £45,000 minus the £12,570 personal allowance, £32,430, all in the basic-rate band, so income tax is £6,486. Class 4 NI is 6% of £32,430 = £1,945.80. The 2025/26 bill is £8,431.80, an effective rate of 18.74%. Because it is over £1,000 and none of it was taxed at source, HMRC also asks for two payments on account towards 2026/27 of £4,215.90 each. On 31 January 2027 this person pays £12,647.70 (the £8,431.80 balance plus the first payment on account), and a further £4,215.90 on 31 July 2027. On £30,000 profit the bill would be £4,531.80 and the January total £6,797.70.
Payments on account surprise many first-year sole traders, because the first January bill can be roughly one and a half times the tax for the year. Each one is half of last year's Self Assessment bill (income tax and Class 4 NI, not student loan or Class 2). You don't have to make them if that bill was under £1,000, or if more than 80% of your tax was collected at source, for example through PAYE. If your profits are falling you can ask HMRC to reduce them, but you will pay interest if the reduced amount turns out too low. The calculator shows whether the rules apply to you and why.
The extras help you plan rather than just get a number: a deadline timeline with HMRC's late filing penalties (£100 straight away, then £10 a day after three months) and late payment penalties of 5% at 30 days, six months and twelve months; a savings plan showing how much to put aside each month to cover 31 January and 31 July; and a pension what-if that shows how much an extra contribution saves you. Higher-rate taxpayers save an extra 20% on every gross pound they pay into a personal pension, claimed back through this return. This is an estimate, not your tax return: it ignores losses brought forward, capital gains, the marriage allowance, foreign income and most reliefs, so check the final figures in your HMRC online account.
How to Use This Calculator
- 1Pick the tax year: 2025/26 for the return due by 31 January 2027, or 2026/27 to plan ahead. Tick Scottish taxpayer if you live in Scotland.
- 2Enter your self-employment profit, or switch to turnover and expenses and choose between your real expenses and the £1,000 trading allowance.
- 3Add any salary with the income tax already deducted through PAYE (from your P60), plus rental profit, savings interest and dividends.
- 4Enter personal pension contributions you paid (the net amount, before your provider adds 20%), Gift Aid donations and any Child Benefit received.
- 5Choose your student loan plan and enter any payments on account you already made for the year.
- 6Read the total to pay on 31 January, the band-by-band breakdown and the deadline timeline, then copy the share link if you want to keep or send the result.