CWF1 (self-employment registration)
UK tax glossary · Last reviewed: April 2026
When you start self-employment, you must notify HMRC using the CWF1 registration process (online via your Government Gateway account). The deadline is 5 October after the end of the tax year in which you started trading.
Registering triggers the issue of your UTR (Unique Taxpayer Reference), enrolment in Self Assessment, and the obligation to pay Class 4 NI through your annual return. Late registration can lead to penalties.
If you are already registered for Self Assessment (for example, as a higher earner or landlord), you simply add self-employment income to your existing return — you do not need to register again using CWF1.
Common questions
What is the penalty for registering late as self-employed?
HMRC can charge a penalty for late notification, though they often waive it if there is a reasonable excuse. The greater risk is failing to file and pay on time once you are registered.
Do I need to register even if my self-employment income is small?
If your profit exceeds £1,000 (the trading allowance), you must register. Below £1,000, the trading allowance means no tax is owed, and registration is optional but recommended to protect your NI record.
Related resources
TaxHelper provides general information based on published HMRC rates and guidance. It is not regulated financial or tax advice. For decisions involving significant sums, complex circumstances, or if you are unsure, speak to a qualified accountant or HMRC directly.