Self Assessment tax estimator
For the self-employed: estimate the income tax and Class 4 National Insurance on your profit, and your payments on account. 2025/26, England.
Your estimate
Estimated tax on your profit
£0
- Income tax
- £0
- Class 4 NIC
- £0
- Total due
- £0
- Set aside per month
- £0
Assumes England rates and the standard personal allowance. Class 4 NIC only (Class 2 is generally treated as paid where profits exceed the threshold). Excludes student loans and the personal-allowance taper above £100,000.
In plain English
The terms, explained
New to this? Here’s what the words on this page actually mean.
- Self Assessment
- The system for telling HMRC about income that isn’t taxed automatically — like self-employment — and paying the tax due.
- Profit
- Your income after allowable business expenses — the figure you’re taxed on.
- Class 4 NIC
- National Insurance the self-employed pay on profits — 6% between £12,570 and £50,270, then 2%.
- Payments on account
- If your bill tops £1,000, HMRC asks for two advance payments towards next year — on 31 January and 31 July.
FAQ
Self Assessment tax estimator — your questions answered
How much tax will I pay on my Self Assessment?
Income tax on your profit above the £12,570 personal allowance (20%, 40% or 45%), plus Class 4 National Insurance at 6% then 2%. The calculator estimates both, plus any payments on account.
What are payments on account?
If your tax bill is over £1,000, HMRC asks for two advance payments towards next year’s bill — half on 31 January and half on 31 July. They catch a lot of people out in their first year, so we always explain your full schedule.
When is my Self Assessment due?
Online returns and any tax owed are due by 31 January following the end of the tax year (which runs to 5 April). We file yours early so you know the figure well in advance.
How much should I set aside for my tax bill?
Often around 20–30% of your profit, but it depends on your income. The calculator gives a monthly “set aside” figure for your exact numbers so the bill never comes as a shock.
Do I need to file a Self Assessment?
Generally yes if you’re self-employed, a landlord, a company director, or have other untaxed income. We’ll confirm whether you need to file and handle the whole return for you.
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