Self Assessment guides
Plain-English explainers on how UK Self Assessment works for the self-employed: tax bands, National Insurance, allowances, deadlines and the SA302 itself.
- SA302 basics
What is an SA302?
What the SA302 tax calculation actually is, when you need one, and how it fits with the Tax Year Overview.
- Mortgages
SA302 vs Tax Year Overview
The two documents mortgage lenders ask self-employed applicants for, and why you need both.
- Tax calculation
How your tax is calculated
The full order of operations behind a Self Assessment bill, with a worked example you can follow.
- National Insurance
Class 2 vs Class 4 NI
The two kinds of National Insurance the self-employed pay, current rates, and the recent cuts.
- Allowances
The £100k allowance taper
Why income between £100,000 and £125,140 is taxed at an effective 60%, and how to soften it.
- Tax planning
Reduce your tax bill
Legitimate ways to lower a Self Assessment bill: pensions, expenses, allowances and timing.
- SA302 basics
How to get your SA302
Step-by-step: printing your SA302 tax calculation and Tax Year Overview from your HMRC account, for every way you might have filed.
- Dividends
Dividend tax by year
Dividend allowances and rates for 2022-23 to 2025-26, and how dividends are taxed on top of other income.
- Savings
Tax on savings interest
The Personal Savings Allowance, the £5,000 starting rate, and when savings interest is actually taxed.
- Expenses
Allowable expenses
What counts as an allowable business expense, the main categories, and the simplified flat rates.
- Property
Property income
What counts as taxable property income, allowable costs, and the mortgage interest rules.
- Filing
Common filing mistakes
The errors that most often change a tax bill or trigger a penalty, and how to avoid them.
- Tax calculation
How much tax will I pay?
A breakdown of what a self-employed person pays at different profit levels, with example figures.
- Payments
Payments on account
Why HMRC asks you to pay next year's tax in advance, how it's worked out, and when to reduce it.
- Deadlines
Key deadlines
The register, file and pay dates for Self Assessment, and the penalties for missing them.
- Planning
Estimate before filing
Why it pays to estimate your tax before you file, and how to get a reliable number early.
- 2025-26
SA302 estimate for 2025-26
What's changed for the 2025-26 tax year and how to estimate your self-employed tax for it.
- Business structure
Sole trader vs limited company
How the tax compares between trading as a sole trader and through a limited company.