Self Assessment for the Self-Employed: A 2026 UK Guide

Short answer: If you are self-employed in the UK and earned more than £1,000 from your trade in a tax year, you must register for Self Assessment with HMRC and file a tax return. Register by 5 October after the end of the tax year. File your online return and pay any tax owed by 31 January; a paper return is due earlier, by 31 October. If your bill is large enough, you also make payments on account on 31 January and 31 July. You pay Income Tax plus Class 4 (and any Class 2) National Insurance through the return.

Self Assessment is simply the system HMRC uses to collect Income Tax and National Insurance from people whose tax is not taken automatically through PAYE. For a sole trader or freelancer, it is the main once-a-year tax job, and good records make it far less stressful.

Who has to register for Self Assessment?

You must register for Self Assessment as a sole trader if your gross trading income in a tax year (6 April to 5 April) was more than £1,000. The £1,000 figure is the trading allowance: if you earned that or less, you usually do not need to report it.

According to GOV.UK, you must still register even under £1,000 in certain cases, for example if you want to:

• Claim relief for a loss on your return
• Pay voluntary Class 2 National Insurance to protect benefit entitlements
• Claim Tax-Free Childcare or Maternity Allowance based on self-employment

You may also need Self Assessment for other reasons (rental income, high income, dividends), but this guide focuses on self-employment.

What are the Self Assessment deadlines for 2026?

Miss a deadline and HMRC charges an automatic penalty, so put these dates in your calendar. The table uses the 2025/26 tax year (6 April 2025 to 5 April 2026) as the worked example.

Task	Deadline	2025/26 tax year date
Register for Self Assessment (new sole traders)	5 October after the tax year ends	5 October 2026
Submit a paper tax return	31 October	31 October 2026
Submit an online tax return	31 January	31 January 2027
Pay the tax you owe (balancing payment)	31 January	31 January 2027
First payment on account	31 January	31 January 2027
Second payment on account	31 July	31 July 2027

Source: GOV.UK, “Self Assessment tax returns: Deadlines” and “Understand your Self Assessment tax bill: Payments on account”.

What are payments on account?

Payments on account are advance payments towards your next tax bill. HMRC asks for them if your Self Assessment bill is £1,000 or more and less than 80% of your tax was collected at source.

• Each payment on account is usually half of your previous year’s tax bill.
• The first is due 31 January (alongside your balancing payment for the prior year).
• The second is due 31 July.
• Class 4 National Insurance is included; Class 2 is not part of payments on account.

For your first year of trading, this can be a shock: you may pay the tax for the year just gone plus the first payment on account for the next year on the same 31 January date. Set money aside early.

How much tax and National Insurance will I pay?

Through Self Assessment, a self-employed person typically pays Income Tax on their profits plus National Insurance.

Charge	2025/26 position	Notes
Income Tax	Standard rates and bands on taxable profit	Personal Allowance applies before tax is due
Class 4 National Insurance	Main rate of 6% on profits between the lower and upper profit limits	An additional 2% applies to profits above the upper limit
Class 2 National Insurance	£3.50 per week for 2025/26	Now generally treated differently since April 2024; see GOV.UK. Voluntary Class 2 can protect benefits if profits are low

Figures such as bands, allowances and thresholds change each year. Verify the current rates on GOV.UK, or use HMRC’s “Estimate your Self Assessment tax bill” tool. This article does not quote every band because they are updated annually.

What records do I need to complete a return?

You cannot fill in an accurate return without your numbers. Keep the following throughout the year:

• Sales and income records (invoices issued, amounts received)
• Business expenses with receipts
• Bank statements for business transactions
• Mileage logs if you claim vehicle costs
• Records of any other taxable income

HMRC requires self-employed people to keep records for at least 5 years after the 31 January submission deadline of the relevant tax year. If HMRC opens a check, these records are your evidence.

How can an app make Self Assessment easier?

The hardest part of Self Assessment is usually not the form; it is having a clean, complete record of your income and expenses ready in January. Capturing everything as it happens removes the year-end panic.

Keel: Invoice Maker & Receipts by Ilura Technology is a private, on-device app for the self-employed. You can create invoices, capture receipts and log business trips, all stored encrypted on your iPhone with no bank connection, no cloud and no account (the App Store lists its data practices as “Data Not Collected”). That means your income and expense records sit in one place on your phone, ready to hand to your accountant or type into your return.

An honest note for UK users: Keel is currently US-centric, so its built-in mileage rate is the IRS rate, not the HMRC rate, and it does not file your Self Assessment for you. Use it for private invoicing, receipt capture and record-keeping; apply UK tax rules at filing time.

A simple Self Assessment checklist

• Confirm you need to file (trade income over £1,000, or another reason)
• Register with HMRC by 5 October after the tax year
• Get your Unique Taxpayer Reference (UTR) and Government Gateway login
• Total your income and allowable expenses
• Note whether payments on account apply to you
• File online by 31 January (or paper by 31 October)
• Pay by 31 January (and 31 July if you have a second payment on account)
• Keep all records for at least 5 years

Frequently asked questions

Do I have to register for Self Assessment if I earn under £1,000? Usually no, thanks to the £1,000 trading allowance. But you must register if you want to claim a loss, pay voluntary Class 2 NIC, or claim certain benefits such as Tax-Free Childcare or Maternity Allowance based on self-employment.

When is the Self Assessment deadline? Online returns and payment are due by 31 January; paper returns by 31 October. New sole traders should register by 5 October after the tax year ends.

What are payments on account? Advance instalments towards next year’s tax, each usually half of your previous bill, due 31 January and 31 July. They apply if your bill is £1,000 or more and most of your tax was not collected at source.

What is Making Tax Digital for Income Tax? From 6 April 2026, sole traders and landlords with qualifying income over £50,000 must keep digital records and send quarterly updates using compatible software. The threshold falls to £30,000 from April 2027 and £20,000 from April 2028. Check “Making Tax Digital for Income Tax” on GOV.UK to see if it affects you.

Can I file Self Assessment myself? Yes, many sole traders file their own return through GOV.UK. For anything complex, or your first year, an accountant is worth the fee.

The bottom line

Self Assessment is manageable if you register on time, know your deadlines (31 October paper, 31 January online and payment, plus 31 July for a second payment on account) and keep clean records all year. Keeping invoices and receipts current, for example in a private app like Keel, turns a January scramble into a quick review. Confirm current rates and thresholds on GOV.UK.

Try Keel on the App Store: https://apps.apple.com/us/app/keel-invoice-maker-receipts/id6786659713 (Free: 3 invoices/month plus unlimited receipts; Pro is roughly the £ equivalent of $7.99/month or $59.99/year, see the App Store for local pricing).

This article is general information, not tax advice. Consult a qualified accountant or tax adviser.