UK Self Assessment Tax Calculator 2026/27
Calculate your 2026/27 UK Self Assessment tax liability. Covers income tax, Class 4 NI contributions, and the payment on account system.
Last updated: May 2026
Gross income from PAYE employment
Net profit after allowable business expenses
Total Income
£50,000
Personal Allowance
£12,570
Taxable Income
£37,430
Income Tax
£7,486
Class 4 NI
£1,046
Total Tax Bill
£8,532
31 January (Tax Year + 1)
Balancing payment + 1st Payment on Account
£12,798
£8,532 + £4,266
31 July (Tax Year + 1)
2nd Payment on Account
£4,266
50% of total tax
Total Tax Year Outflow
First year (no prior POA)
£17,064
* Payments on account apply when your Self-Assessment tax bill exceeds £1,000 and less than 80% is collected at source. The January payment shown includes a first-year scenario where you also pay the current year's balancing payment plus the first POA for the next year. Subsequent years differ.
Reviewed by Vikram Malhotra
•Mortgage Specialist & Ex-BankerWith over 15 years in retail banking, Vikram provides deep insights into bank-specific interest rate tiering and processing fee structures for home and personal loans. All mathematical models and regulatory data points have been verified for the current 2026 fiscal period.
What is Self Assessment in the UK?
Self Assessment is HMRC's system for collecting income tax from people who are self-employed, have multiple income sources, or earn above certain thresholds. You must file a tax return each year showing your income and calculate the tax owed.
Self-employed people pay income tax on profits, Class 2 NI (now collected through Self Assessment), and Class 4 NI on profits. Payments on account (advance tax payments) are required if your tax bill exceeds £1,000.
How to use this calculator
- 1Enter trading profit — Input your total self-employed income minus allowable business expenses.
- 2Add other income — Include any employment income, savings interest, or rental income.
- 3Review tax breakdown — See income tax, Class 4 NI, and any payments on account due.
- 4Plan your payments — Note the January 31 and July 31 payment deadlines.
Formula & example
Tax Owed = Income Tax + Class 4 NI - Tax Already Paid | Payment on Account = 50% of previous year tax bill x 2 payments
Example: Self-employed profit of 50,000. Income tax = 7,486. Class 4 NI = 2,228. Total tax = 9,714. First payment on account due January 31 = 4,857.
Benefits
Full liability calculation
Shows income tax, NI, and payment on account in one place.
Expense planning
See how additional allowable expenses reduce your tax bill.
Payment schedule
Understand when each payment is due to avoid interest charges.
2026/27 rates
Uses current tax bands, NI thresholds, and personal allowance.
Use cases
Freelancers and consultants
Calculate the quarterly tax set-aside needed to meet your Self Assessment bill.
Sole traders
Estimate tax before the January 31 deadline to avoid surprises.
Landlords
Include rental income alongside self-employment profits in your tax calculation.
Side income
Calculate additional tax owed when you have employment income plus a side business.
Frequently asked questions
When is the Self Assessment deadline for 2026/27?+
The paper return deadline is October 31. Online returns must be filed by January 31 following the end of the tax year. The January 31 deadline also coincides with the payment deadline for any tax owed and the first payment on account.
What are payments on account?+
If your Self Assessment tax bill exceeds £1,000, you must make two advance payments toward next year's bill. The first is due January 31 and the second July 31, each equal to 50% of your previous year's bill.
What expenses can I deduct?+
You can deduct expenses wholly and exclusively for business use: office costs, travel, staff wages, professional fees, marketing, equipment depreciation, and a portion of home working costs if you work from home.
Do I need to file a Self Assessment return?+
You must file if you are self-employed with profits above £1,000, a company director, earn over £100,000, have untaxed income above £2,500, or receive Child Benefit and earn over £60,000.
What is the penalty for filing late?+
A £100 fixed penalty applies immediately after the January 31 deadline. After 3 months, daily penalties of £10 per day accumulate for up to 90 days. After 6 and 12 months, further 5% penalties on the tax owed apply.