Useful next calculations
Rates and sources, 2026/27
2026/27 Income Tax and Class 4 NI reserve estimate. Payments on account are shown as advance cash requirements and are not added to the tax liability.
| Band or figure | Rate |
|---|---|
| Class 4 main rate | 6% |
| Class 4 additional rate | 2% |
| Payment-on-account instalments | normally 50% each |
| Normal due dates | 31 January / 31 July |
Source: HMRC — self-employed National Insurance. Source checked for 2026/27.
When to use this calculator
- Before accepting a pay change, bonus, pension contribution or salary-sacrifice option.
- When you want a simple take-home estimate before payroll or filing.
- When you are approaching the £100,000 income level and want to see the personal allowance taper.
- When you need to convert between hourly, monthly and annual pay.
A worked example
These are the example figures the calculator opens with.
| Input | Value |
|---|---|
| Forecast taxable self-employed profit (£) | £50,000 |
| Other non-savings taxable income (£) | £0 |
| Gross pension contributions + grossed-up Gift Aid (£) | £0 |
| Income Tax already deducted at source (£) | £0 |
For those figures the calculator returns:
- Estimated income tax: £7,486.00
- Estimated Class 4 NI: £2,245.80
- Current-year Self Assessment amount after tax deducted: £9,731.80
- Remaining balancing payment: £9,731.80
- Each modelled payment on account: £4,865.90
- January cash target: £14,597.70
- July cash target: £4,865.90
- Monthly current-year reserve: £810.98
- Reserve as share of profit: 19.46%
How to read your results
Estimated Income Tax
Review this figure alongside your gross income so you can understand deductions before the tax year closes. It is a planning estimate, not a filed return.
Current-Year Self Assessment Amount After Tax Deducted
Review this figure alongside your gross income so you can understand deductions before the tax year closes. It is a planning estimate, not a filed return.
Method & assumptions
This planner estimates 2026/27 Income Tax on the profit and other non-savings income entered, then adds Class 4 National Insurance when selected and subtracts tax already deducted at source. Payments on account already made reduce the remaining balancing payment.
The monthly reserve covers the estimated current-year Self Assessment amount. When payments on account are selected, the January cash target adds one half of that amount as a proxy for the next year's first payment; the July target shows the second half. Those advances are not counted as extra tax.
HMRC uses the filed previous-year return and detailed relevant-amount rules. This estimate excludes VAT, student loans, CGT, HICBC, Class 2 choices, penalties, interest and many reliefs. Use the HMRC statement and reduce payments on account only when there is a reasonable basis, because an excessive reduction can attract interest.
Common mistakes
- Entering gross income when you really want take-home pay, or vice versa.
- Ignoring pension contributions, deductions or local tax rules that change the result.
- Comparing monthly and annual figures without standardising them first.
- Overlooking National Insurance or student-loan plan differences that apply to you.
What to do next
- Check the same scenario with related pay or deduction calculators.
- Keep a copy of the assumptions so you can compare the next tax year or pay period.
- If you are self-employed, compare this result with the self-employment tax calculator.
- Check whether a small pension contribution change moves take-home pay more than you expect.