When you start working for yourself as a sole trader, you must register with HMRC for Self Assessment. This is how the government tracks your income and collects the tax you owe.

Registration is straightforward but you must do it by the deadline to avoid penalties. Once registered, you will receive a Unique Taxpayer Reference (UTR) - a 10-digit number that identifies you for tax purposes.

Do you need to register?

You must register for Self Assessment if you earned more than the trading allowance from self-employment. You may also want to register even if you earn less, to prove your self-employed status for mortgages or benefit claims.

Self Assessment registration requirements

Registration threshold, deadline, and UTR delivery times for self-employed individuals.

You must register for Self Assessment with HMRC if you earn more than the trading allowance from self-employment. Registration is done online through Government Gateway and results in a Unique Taxpayer Reference (UTR) being posted to you.

Registration threshold: More than £1,000 from self-employment in a tax year
Registration deadline: 5 October following the end of your first tax year
UTR delivery (UK residents): 10-15 working days by post
UTR delivery (overseas residents): 21 working days by post
UTR format: 10-digit number (may be called 'tax reference' on some letters)
Tax year dates: 6 April to 5 April

When you must register

You earned more than £1,000 from self-employment
You want to make voluntary Class 2 National Insurance contributions
You need to prove you are self-employed (for benefits or other purposes)
You want to register as a Construction Industry Scheme (CIS) subcontractor

What is a UTR?

Your Unique Taxpayer Reference is issued for life - it will not change even if your circumstances do. You will need it to file tax returns, access HMRC online services, and for some business transactions.

What is a Unique Taxpayer Reference (UTR)

Definition and format of the UTR number issued by HMRC.

A Unique Taxpayer Reference (UTR) is a 10-digit number issued by HMRC to identify a person or business entity for tax purposes. It is issued for life and remains the same regardless of changes to your circumstances.

UTR format: 10-digit number (sometimes with letter 'K' suffix)
Example format: 1234567890 or 1234567890K
Issued by: HM Revenue and Customs (HMRC)
Validity: Issued for life - does not change or expire

Important distinction

Do not confuse UTR with your Government Gateway user ID:

UTR: 10 digits - identifies your tax records
Government Gateway ID: 12 digits - used to log in to HMRC online services

Find your UTR number

When will you receive your UTR?

HMRC sends your UTR by post for security reasons. They will never email it or give it over the phone. Allow time for delivery before your first tax return is due.

UTR delivery timelines

How long it takes to receive a UTR after registering with HMRC. Pure data reference.

UTR numbers are always sent by post for security reasons. HMRC will never send your UTR by email or give it over the phone.

Self-employed (online registration, UK): 10 working days
Self-employed (online registration, overseas): 21 working days
Non-self-employed (SA1 form): 21 days (may be longer during busy periods)
Partnership (online): 10-15 working days
Partnership (postal): 15 working days
Limited company (CT41G letter): Within 1 month of Companies House registration

Activation code

An activation code is sent separately from your UTR. You need this code to activate your HMRC online account.

Activation code delivery (UK): Within 10 working days
Activation code delivery (overseas): Within 21 working days
Activation code validity: Must be used within 28 days

Check when you can expect a reply from HMRC

Registration deadlines

Missing the registration deadline can result in penalties, even if you do not owe any tax. Register early to ensure you receive your UTR in time to file your first tax return.

UTR registration deadlines

Deadlines for registering for Self Assessment and obtaining a UTR.

You must register for Self Assessment (and obtain a UTR) by specific deadlines to avoid penalties.

Self-employed/individuals registration deadline: 5 October following the end of the tax year in which you started trading
Example (2024/25 tax year): Started trading in 2024/25 (6 April 2024 - 5 April 2025) - register by 5 October 2025
Partnership registration deadline: 5 October in the business's second tax year
Limited company notification deadline: Within 3 months of starting business activity
Late registration: May result in a penalty from HMRC

Self Assessment filing deadlines

Once registered, you must file your tax return and pay any tax owed by these deadlines:

Paper tax return: 31 October
Online tax return: 31 January
Payment deadline: 31 January
Payment on account (if applicable): 31 July

Self Assessment tax returns: deadlines

Failure to notify penalties

HMRC penalty ranges for failing to register for Self Assessment when required.

If you fail to tell HMRC that you need to register for Self Assessment, you may be charged a 'failure to notify' penalty. The penalty is a percentage of the tax you should have paid. The amount depends on whether you come forward voluntarily or HMRC discovers the failure, and how long after the deadline this happens.

Non-deliberate, unprompted, within 12 months: 0-30% of potential lost revenue
Non-deliberate, prompted, within 12 months: 10-30% of potential lost revenue
Non-deliberate, unprompted, after 12 months: 10-30% of potential lost revenue
Non-deliberate, prompted, after 12 months: 20-30% of potential lost revenue
Deliberate, unprompted: 20-70% of potential lost revenue
Deliberate, prompted: 35-70% of potential lost revenue
Deliberate and concealed, unprompted: 30-100% of potential lost revenue
Deliberate and concealed, prompted: 50-100% of potential lost revenue

Key terms

Unprompted: You tell HMRC about the failure before they contact you about it
Prompted: HMRC discovers the failure or contacts you first
Potential lost revenue: The tax you should have paid but did not

Coming forward voluntarily (unprompted) always results in a lower penalty. HMRC also considers your cooperation and the quality of your disclosure when setting the penalty within the range.

Failure to notify penalties (CC/FS11)

National Insurance for the self-employed

As a sole trader, you pay Class 2 and Class 4 National Insurance on your profits. Class 2 is a flat weekly amount that protects your State Pension entitlement. Class 4 is calculated as a percentage of your profits above certain thresholds.

Understanding these rates helps you budget for your tax bill and plan for retirement.

Self-employed National Insurance rates 2025/26

Class 2 and Class 4 NI rates and thresholds for self-employed individuals.

Self-employed individuals pay Class 2 and Class 4 National Insurance on their profits. Class 2 is a flat weekly rate that builds your State Pension entitlement. Class 4 is a percentage of your profits above certain thresholds.

Class 2 NI weekly rate: £3.50 per week
Small Profits Threshold: £6,845 per year (Class 2 voluntary below this)
Class 4 NI main rate: 6% on profits between £12,570 and £50,270
Class 4 NI additional rate: 2% on profits above £50,270
Class 4 Lower Profits Limit: £12,570 per year
Class 4 Upper Profits Limit: £50,270 per year
Effective from: 6 April 2025

How Class 2 works

If your profits are below £6,845, Class 2 is voluntary but you may choose to pay it to protect your State Pension and benefit entitlement. If your profits are £6,845 or more, Class 2 is treated as paid automatically (you do not need to pay separately).

Self-employed National Insurance rates

What happens after you register

Once you have registered and received your UTR:

Set up your HMRC online account - You will receive an activation code separately (within 10 working days). Use this to access your online Self Assessment account.
Keep records of income and expenses - You will need these to complete your tax return. Keep records for at least 5 years.
File your tax return by 31 January - This is for the previous tax year (6 April to 5 April). For example, for 2024/25, file by 31 January 2026.
Pay your tax bill by 31 January - You may also need to make payments on account (advance payments) by 31 July.

Common mistakes to avoid

Registering too late - You must register by 5 October following the end of your first tax year of trading, not by your first tax return deadline.
Waiting for your UTR to arrive - If it has been more than 10 working days (21 days if overseas), contact HMRC. Do not wait until your tax return is due.
Confusing UTR with Government Gateway ID - Your UTR is 10 digits and identifies your tax records. Your Government Gateway ID is 12 characters and is used to log in to HMRC services.
Not keeping records - HMRC can charge penalties of up to £3,000 per tax year for inadequate record-keeping.

Check if you need to register

If you earned more than £1,000 from self-employment in a tax year, you must register. Below £1,000, registration is optional but useful for proving self-employed status.
Register online with HMRC

Use the Government Gateway to register for Self Assessment. You will need your National Insurance number and personal details.
Wait for your UTR to arrive

Your UTR will be posted within 10 working days (UK) or 21 working days (overseas). Keep this number safe - you need it for all Self Assessment activity.
Activate your online account

An activation code will arrive separately. Use it within 28 days to set up your online Self Assessment account.
Set up record-keeping

Start tracking income and expenses from day one. Use accounting software or a spreadsheet to make tax returns easier.

THRESHOLD £1,000

turnover threshold: £1,000

If your total self-employment income is £1,000 or less in the tax year, you do not need to register for Self Assessment or tell HMRC about this income.

Above threshold:

You must register for Self Assessment by 5 October following the end of the tax year you started trading.

Below threshold:

The trading allowance automatically applies. You have no tax liability and no need to file a return for this income alone.

Strategic considerations: You may still want to register even below the threshold to prove self-employed status for mortgages, benefit claims, or to pay voluntary Class 2 NI for State Pension credits.

Compliance timeline: Registration deadline is 5 October following your first tax year of trading

Business Context Testing

Content Graph

Guvnor

Register as self-employed with HMRC

Do you need to register?

What is a UTR?

When will you receive your UTR?

Registration deadlines

National Insurance for the self-employed

What happens after you register

Common mistakes to avoid

Check if you need to register

Register online with HMRC

Wait for your UTR to arrive

Activate your online account

Set up record-keeping

Trading allowance - you may not need to register

Above threshold:

Below threshold:

Compliance Assistant

🧪 Business Context Testing

◉ Content Graph

Do you need to register?

What is a UTR?

When will you receive your UTR?

Registration deadlines

National Insurance for the self-employed

What happens after you register

Common mistakes to avoid

Check if you need to register

Register online with HMRC

Wait for your UTR to arrive

Activate your online account

Set up record-keeping

Trading allowance - you may not need to register

Above threshold:

Below threshold:

Related guides in Tax & Finance

Business Context Testing

Content Graph