Estimate your tax bill before January arrives. Covers income tax, Class 2 & 4 National Insurance, and payments on account.
Your Income & Expenses
£
Your gross income from self-employment / freelance
£
Business costs you can deduct (equipment, travel, etc.)
£
Salary or pension already taxed at source
£
Income tax already deducted from PAYE income
Your Tax Bill
Total Tax & NI Due
—
for the 2025–26 tax year
Income Tax
—
NI (Class 2 + 4)
—
Take-Home (Self-Emp)
—
Tax Breakdown
Component
Taxable Amount
Rate
Tax Due
Payments on Account
31 Jan 2026
—
Balancing payment + 1st PoA
31 Jul 2026
—
2nd Payment on Account
31 Jan 2027
—
Balancing payment + 1st PoA
Estimate only. This calculator uses 2025–26 rates for England, Wales, Northern Ireland, and Scotland. It does not account for pension contributions, Gift Aid, capital gains, rental income, or other reliefs. Class 2 NI is £3.45/week if profits exceed £12,570. Always complete your actual Self Assessment return on HMRC's website before 31 January.
Self Assessment Guide
Who needs to file Self Assessment?
You must file a Self Assessment tax return if you're self-employed, a sole trader, or have untaxed income above £1,000 — even if you also have a regular PAYE job. The deadline is 31 January each year for the previous tax year.
01
Class 2 & Class 4 NI
Self-employed people pay two types of NI. Class 2 is a flat £3.45/week if profits exceed £12,570. Class 4 is 6% on profits between £12,570–£50,270, and 2% above that. Both are calculated via Self Assessment.
02
Allowable expenses
You can deduct genuine business costs — office supplies, travel, software, professional fees, a portion of home costs if you work from home. You cannot deduct personal expenses, fines, or anything not "wholly and exclusively" for business.
03
Payments on Account
If your tax bill exceeds £1,000, HMRC requires advance payments towards next year's bill. You pay 50% on 31 January and 50% on 31 July. This catches many first-year freelancers off guard — your January bill can be 1.5× the actual tax owed.
04
Deadlines & penalties
Register for Self Assessment by 5 October if you're new. File online by 31 January. A day late costs £100. Three months late adds £10/day. Missing the payment deadline incurs 5% interest. Don't leave it to January.
Frequently Asked Questions
What's the trading allowance?
If your self-employment income is under £1,000 in the tax year, it's covered by the trading allowance and you don't need to file or pay tax on it. Above £1,000, you must register and file.
Can I reduce my tax bill with pension contributions?
Yes — contributions to a personal pension (SIPP) get tax relief at your marginal rate. This is one of the most effective ways to reduce your Self Assessment bill legally. Each £100 paid in costs a basic-rate taxpayer just £80 after relief.
Do I pay NI as well as income tax?
Yes. As a self-employed person you pay Class 4 NI (6% on profits £12,570–£50,270, 2% above) plus Class 2 NI (£3.45/week). You do not pay Class 1 NI (the employee/employer NI on salaries). Your NI payments count towards the State Pension.
What if I can't pay my tax bill?
Contact HMRC before the deadline — don't ignore it. They offer Time to Pay arrangements allowing you to spread payments over several months. Penalties for not filing are separate from not paying, so always file on time even if you can't pay immediately.