Tax Set-Aside Calculator UK 2026/27
Work out how much to save each month for your Self Assessment tax bill
How much should I save for tax?
As a self-employed person or sole trader in 2026/27, you pay income tax and Class 4 National Insurance on your profits. HMRC collects this through Self Assessment, with your annual bill due on 31 January. Most self-employed people should set aside 25–35% of their profit as a safe guide, though the exact amount depends on your profit level, expenses, and any other income.
What is Payments on Account?
If your Self Assessment bill exceeds £1,000, HMRC requires you to make Payments on Account — advance payments towards your next year’s bill. Each payment is 50% of your previous bill, due 31 January and 31 July. This means your first year’s tax payment could be 150% of your actual bill. This calculator warns you if this applies.
Frequently asked questions
You pay income tax at 20% on profits between £12,570 and £50,270, and 40% above that. You also pay Class 4 National Insurance at 9% between £12,570 and £50,270, and 2% above that. The first £12,570 of profit is tax-free (Personal Allowance).
Your annual Self Assessment bill is due on 31 January following the end of the tax year. For the 2025/26 tax year, the deadline is 31 January 2027. If you also have Payments on Account, a further payment is due 31 July.
A commonly recommended rule is to set aside 25–35% of your self-employed income. Lower earners closer to the personal allowance may need less; higher earners above £50,270 should set aside more. This calculator gives you a precise figure based on your actual profit.
Class 4 NI is charged at 9% on profits between £12,570 and £50,270, and 2% on profits above £50,270. Class 2 NI was abolished from April 2024.
Worked example
A freelance designer earns £35,000 and has £5,000 of allowable expenses, giving a taxable profit of £30,000. They have 7 months until the January deadline:
| Taxable profit (£35,000 − £5,000) | £30,000 |
| Personal Allowance | −£12,570 |
| Taxable amount | £17,430 |
| Income tax (20%) | £3,486 |
| Class 4 NI (9% on £17,430) | £1,569 |
| Total Self Assessment bill | £5,055 |
| Monthly set-aside (÷ 7 months) | £722 |
| Weekly set-aside | £167 |
Payments on Account will apply as the bill exceeds £1,000 — the first January payment would be £7,582 (bill + 50% POA).
How the calculation works
This calculator uses the 2026/27 HMRC Self Assessment tax calculation method:
- Net profit: Income minus allowable business expenses
- Personal Allowance: First £12,570 of total income is tax-free
- Income tax: 20% on £12,570–£50,270, 40% above, 45% above £125,140
- Class 4 NI: 9% on profits £12,570–£50,270, 2% above (Class 2 abolished April 2024)
- Payments on Account: If bill exceeds £1,000, HMRC requires advance payments of 50% each in January and July
All calculations run entirely in your browser. No data is sent to our servers, stored, or shared with any third party.
Results are estimates based on 2026/27 HMRC rates and are intended as a guide only. They do not constitute financial or tax advice. Always verify with HMRC or a qualified accountant for your specific circumstances.