What is the CWF1 Form? A Guide for the Self-Employed

/Published:24th December 2025/inBusiness, Making Tax Digital, Running a business, Self Employed
Accounting Wise - What is the CWF1 Form

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If you’re taking your first steps into self-employment in the UK, one of the earliest (and most important) admin tasks on your list is registering with HMRC. This ensures you’re officially set up for Self-Assessment and paying the correct National Insurance contributions, which ultimately count towards your State Pension and other benefits.

That’s where the CWF1 form comes in.

The CWF1 form is HMRC’s official notification that you’ve started working for yourself. Whether you’re a sole trader, freelancer, contractor or running a small side business, completing this form creates your tax record with HMRC, enables you to file your annual Self-Assessment tax return, and ensures your National Insurance is tracked correctly.

In this post, we’ll walk you through everything you need to know, including:

  • What the CWF1 form is and why it matters
  • When you need to submit it (and what happens if you don’t)
  • How to complete the form step by step
  • The most common mistakes people make when registering
  • Useful links, resources, and tips to make the process smoother

By the end, you’ll understand exactly what the CWF1 form does, how to complete it correctly, and how it fits into your wider responsibilities as a self-employed business owner.

Tip: You must submit the CWF1 form by 5 October following the end of the tax year in which you started trading. Missing this deadline can result in penalties and make it harder to file your first Self-Assessment return on time.

Helpful Resources:

What is the CWF1 Form?

The CWF1 form is HMRC’s official method of registering as self-employed in the UK. If you’re becoming a sole trader, freelancer, or contractor, this step is essential. It creates your tax record with HMRC, ensures you’re set up correctly for Self Assessment, and makes sure your National Insurance contributions are logged from day one.

By completing the form, you:

  • Notify HMRC that you’ve begun working for yourself.
  • Register for Self Assessment so you can file your annual tax return and report your income, expenses, and allowable deductions.
  • Register for Class 2 National Insurance contributions, which help you build entitlement to the State Pension, Maternity Allowance, and certain other welfare benefits.

Why it matters

If you fail to submit the CWF1 form (or complete the online registration process), HMRC has no way of knowing that you are self-employed. This can result in serious issues, including:

  • Not declaring your income correctly, which can trigger HMRC investigations.
  • Penalty charges for late registration or late filing.
  • Gaps in your National Insurance record, which may reduce future State Pension entitlement.

Expert Insight: Many new sole traders assume that simply earning money makes HMRC aware of their business activity. It doesn’t. You must actively register using the CWF1 form or the online “Register for Self Assessment” process. HMRC will not contact you automatically.

Tip: The simplest way to register is online via your HMRC Government Gateway account. Online registration is quicker, allows you to track progress, and provides instant confirmation that your details have been received.

Useful Resources:
– Register if you’re self-employed – GOV.UK
– Download the CWF1 paper form (HMRC)
– Create or access your Government Gateway account

When Do You Need to Complete a CWF1 Form?

You must complete the CWF1 form as soon as you begin working for yourself and fall within HMRC’s self-employment registration rules. You are required to register if you:

  • Earn more than £1,000 in a tax year from self-employment (this exceeds HMRC’s trading allowance).
  • Start working for yourself as a sole trader, freelancer, or contractor, even if it’s part-time or alongside employment.
  • Join a business partnership – each partner must register separately for Self Assessment.

The registration deadline

You must complete the CWF1 form by 5 October following the end of the tax year in which you became self-employed.

  • The UK tax year runs from 6 April to 5 April.
  • Example: If you started trading in July 2025, this falls within the 2025/26 tax year. You must register by 5 October 2026.

What happens if you miss the deadline?

Missing the registration deadline can lead to:

  • Penalties from HMRC for failing to notify your tax liability on time.
  • Interest charges if tax is paid late due to delayed registration.
  • Delays in setting up your Self Assessment account, which could make it harder to submit your first tax return by 31 January.

Expert Insight: HMRC does not automatically know when someone starts self-employment. Even small side incomes, such as selling crafts online or providing occasional freelance services, can trigger the requirement to register if they exceed £1,000.

Tip: Do not leave registration until October. After submitting your CWF1, HMRC will send your Unique Taxpayer Reference (UTR) through the post – a process that can take several weeks. Registering early gives you more time to prepare your accounts and understand your tax obligations.

Useful Resource: Self Assessment deadlines – GOV.UK

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How to Complete the CWF1 Form Online

Although paper forms still exist, HMRC now encourages most new sole traders to complete the CWF1 registration process online. This is the quickest, most secure, and most reliable way to register for Self Assessment and Class 2 National Insurance. Here’s how to do it step by step:

Step 1: Visit HMRC’s Registration Page

Head to the official Register for Self Assessment if you’re self-employed page on GOV.UK.
You’ll need to sign in with (or create) a Government Gateway account to begin the registration.

Tip: Creating a Government Gateway account requires identity verification. Make sure you have documents such as your passport or driving licence ready.

Step 2: Provide Your Personal and Business Details

You will be asked to enter key information, including:

  • Your National Insurance number
  • Your full legal name, date of birth, and current address
  • The date you started self-employment – this determines the tax year you are registering for
  • Your business details, such as your trading name (if applicable), business address, and a description of the work you carry out

Helpful Note: Your “business description” should be clear and specific. For example: – “Freelance graphic designer” – “Self-employed electrician” – “Online retail seller (e-commerce)” This helps HMRC correctly classify your business activity.

Step 3: Submit the Form Online

Once all your information is entered, submit the form electronically. HMRC will send an on-screen confirmation and, in most cases, an email acknowledgement confirming that your registration is being processed.

Step 4: Wait for Your Unique Taxpayer Reference (UTR)

Within 10–21 days, HMRC will send your 10-digit Unique Taxpayer Reference (UTR) by post to the address you provided.
This number is essential for:

  • Filing your Self Assessment tax return
  • Making tax payments
  • Accessing your HMRC online account
  • Speaking to HMRC about your self-employed taxes

Important: You cannot file a Self Assessment tax return without your UTR.

Pro Tips

  • Register early: Delays in receiving your UTR can cause problems close to the tax return deadline.
  • Keep all HMRC letters safe: Your UTR is unique and does not change – you will use it throughout your entire self-employment journey.
  • Update your address: If you move home after registering, notify HMRC immediately to ensure you don’t miss important correspondence.
  • Use the HMRC app: You can view your tax account, National Insurance record, and deadlines conveniently on the official HMRC app.

Useful Resource: Register if you’re self-employed – GOV.UK

What Happens After Submitting a CWF1 Form?

Once you’ve submitted your CWF1 form and HMRC has confirmed your registration, several ongoing tax and compliance responsibilities begin. These apply whether your self-employment is full-time, part-time, or a side business.

  • Annual Self Assessment tax returns
    Registering means HMRC now expects you to file a Self Assessment tax return every year – even if you make a loss or earn less than your personal allowance.

    The filing deadline for online returns is 31 January following the end of the tax year. Example: For the 2025/26 tax year, your online return must be filed by 31 January 2027.

  • Paying Income Tax and National Insurance
    You will pay tax based on your profits (not your turnover). The key elements are:

    • Income Tax on profits above the personal allowance (£12,570 for 2025/26).
    • Class 2 National Insurance – only payable if profits exceed £12,570 (currently £3.45 per week).
    • Class 4 National Insurance – payable on profits over £12,570 (9% up to £50,270, then 2% on anything above that).

    Note: Class 2 NIC is now collected through Self Assessment rather than paid separately.

  • Record-keeping duties
    You must keep accurate, organised financial records, including:

    • Invoices and receipts
    • Bank statements
    • Expense records
    • Mileage logs and cashbooks (if applicable)

    HMRC requires you to keep records for at least five years after the 31 January deadline for the relevant tax year.
    Accurate records also make completing your tax return significantly easier and reduce the risk of errors or penalties.

  • VAT registration (if required)
    If your taxable turnover exceeds £90,000 (the VAT threshold from April 2025), you must register for VAT.
    You can also register voluntarily below this threshold – often useful for businesses purchasing significant equipment or trading B2B.

Expert Insight: Many new sole traders underestimate how quickly tax liabilities build up. A simple cashflow habit – such as saving 20–30% of each payment you receive – can ensure you’re never caught out at the January deadline.

Tip: After your first tax return, HMRC may require Payments on Account. These are advance payments towards your next year’s bill and are based on your current year’s tax. They often surprise new self-employed taxpayers, so budgeting early can prevent cash flow problems.

Useful Resources:

Common Mistakes to Avoid

Filling out the CWF1 form is usually straightforward, but many new sole traders unintentionally make errors that create problems later on – from missed deadlines to tax return complications. Here are the most frequent mistakes and how to avoid them.

  1. Missing the registration deadline
    You must register as self-employed by 5 October following the end of the tax year in which you started trading. Missing this can lead to late-notification penalties and may compress the time you have to submit your first Self Assessment return.
    Fix: Register as soon as you begin trading rather than waiting until you hit the £1,000 trading allowance threshold or the October deadline.
  2. Entering the wrong business start date
    Your start date determines which tax year your Self Assessment applies to and affects how HMRC calculates your tax. Using the wrong date can mean completing the wrong year’s return or receiving incorrect tax calculations.

    Fix: Use the date you first completed paid work or were genuinely “open for business”. Buying equipment, drafting a logo, or opening a bank account does not count as your start date.

  3. Confusing the CWF1 form with limited company registration
    The CWF1 form is only for sole traders and partners in a partnership. If you intend to operate as a limited company, you must register your business with Companies House and separately register for Corporation Tax with HMRC – you do not complete a CWF1.

    Fix: Confirm your business structure before registering. If unsure, speak with an accountant to avoid using the wrong registration route.

  4. Not setting up your HMRC online account after receiving your UTR
    Once your registration is processed, HMRC sends your Unique Taxpayer Reference (UTR) by post. Many new sole traders mistakenly believe this completes the process – but you must still set up or link your Government Gateway account to file your tax return online.

    Fix: As soon as your UTR arrives, log in or create your HMRC online account and complete the digital setup for Self Assessment.

  5. Using vague or inaccurate business descriptions
    HMRC uses your business description to classify your work. An unclear description can cause issues when reviewing expenses or tax queries.

    Fix: Use clear, specific terms – e.g. “plumbing and heating engineer”, “freelance copywriter”, “online retail trader”.

  6. Failing to update HMRC when personal details change
    Missing HMRC letters – particularly your UTR or activation codes – can delay access to your account and filing.

    Fix: Update your address, email, and phone number promptly using your Government Gateway or the official HMRC app.

Tip: Keep copies of all HMRC correspondence, especially your UTR letter. Replacing a lost UTR can take time – and without it, you cannot file a tax return or access key parts of your HMRC account.

Useful Resource: Register if you’re self-employed – GOV.UK

Why Use an Accountant for Self-Employed Registration?

While the CWF1 form online process is relatively simple, many new sole traders prefer to work with an accountant to ensure everything is done correctly from the start. Registering properly is the foundation of your tax obligations, so getting it wrong can lead to penalties, missed deadlines, or unnecessary stress later on.

Working with an accountant helps you:

  • Register correctly with HMRC Ensure your details, start date, business description and National Insurance setup are accurate first time.
  • Avoid missing key deadlines
    Accountants track Self Assessment and HMRC timelines for you, reducing the risk of penalties or late filings.
  • Understand your ongoing tax responsibilities
    A professional can explain how Income Tax, Class 2 and Class 4 National Insurance work, what records you need, and how to prepare for your first tax return with confidence.
  • Set up strong bookkeeping systems
    Good record-keeping is essential. An accountant can help you choose tools, create workflows, and understand what you can and cannot claim.
  • Get ongoing support with tax returns
    Your first tax return can feel daunting. Having an expert on hand to prepare, check, and file everything correctly saves time and reduces risk.

Why choose Accounting Wise?

At Accounting Wise, we make self-employed registration simple. We handle the entire HMRC process, ensure full compliance from day one, and give you the ongoing guidance you need to manage your tax obligations confidently. From setting up your registration to supporting your bookkeeping and annual returns, we’re here every step of the way.

CWF1 Conclusion

The CWF1 form is your essential first step into the world of self-employment. Completing it online ensures HMRC has the correct information about your new business, sets up your Self Assessment record, and makes sure your National Insurance contributions are tracked properly from day one.

While the process may feel like routine admin, it plays a crucial role in keeping you compliant, avoiding penalties, and ensuring your tax affairs run smoothly as your business grows. Getting it right early on makes everything that follows far easier.

Need help with your accounts as Sole Trader? Contact Accounting Wise Today!

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CWF1 Form FAQ

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Yes, if your self-employed income exceeds the £1,000 trading allowance within a tax year, you must register with HMRC using the CWF1 process.

Your start date is the day you first carried out paid work or were genuinely trading. It is not the date you bought equipment or created a website.

HMRC typically takes 10–21 days to send your Unique Taxpayer Reference (UTR) by post. It may take longer during busy periods.

Yes, you can start working immediately, but you must register by 5 October following the end of the tax year in which you began trading.

HMRC may issue late-notification penalties, and you may face difficulties completing your first tax return on time.

Yes. Once registered, you must complete a Self Assessment return every year, even if your profit is low or negative.

You do not complete a CWF1. Limited companies register with Companies House and then register separately for Corporation Tax with HMRC.

Absolutely. An accountant can complete the CWF1 form on your behalf, set you up correctly with HMRC, and guide you through the ongoing tax and record-keeping requirements.

Glossary of Key Self-Employment & HMRC Terms

CWF1 Form – HMRC’s official form for registering as self-employed. Completing it notifies HMRC that you’ve started trading and sets you up for Self Assessment and National Insurance.

Self Assessment – The tax system used by HMRC where self-employed individuals report their income and expenses each year. Filed annually, usually by 31 January for online returns.

UTR (Unique Taxpayer Reference) – A 10-digit number assigned by HMRC after you register for Self Assessment. Required for filing tax returns and dealing with HMRC about your taxes.

Government Gateway Account – Your secure online HMRC account used to register for Self Assessment, view tax information, file returns, and manage National Insurance.

Trading Allowance – A £1,000 annual allowance for small amounts of self-employed income. If you earn over this, you must register for Self Assessment using the CWF1 process.

Start Date of Self-Employment – The date you first carried out paid work or were genuinely “open for business.” HMRC uses this to determine your registration deadlines and tax year.

Class 2 National Insurance – A flat-rate contribution paid through Self Assessment if your profits exceed £12,570 (2025/26). Counts towards benefits such as the State Pension.

Class 4 National Insurance – A tax on self-employment profits over £12,570 (9% up to £50,270, then 2% above that), also collected via Self Assessment.

Personal Allowance – The amount you can earn each tax year before paying Income Tax (£12,570 for 2025/26).

Payments on Account – Advance payments towards next year's tax bill. HMRC requires these from many new sole traders after their first tax return, which can affect cash flow.

Tax Year – The period HMRC uses for calculating tax: 6 April to 5 April each year.

Record-Keeping – The legal requirement to keep accurate income and expense records for at least five years after the 31 January deadline for the relevant tax year.

HMRC – His Majesty’s Revenue and Customs, the UK tax authority responsible for Self Assessment, National Insurance, tax collection, and compliance.

VAT Threshold – The turnover point at which you must register for VAT. Set at £90,000 from April 2025.

Sole Trader – The simplest UK business structure where you and the business are legally the same entity. Easy to start, but the sole trader is personally liable for business debts.

Partnership – A business structure where two or more people share profits and responsibilities. Each partner must register for Self Assessment individually.

Allowable Expenses – Business costs you can deduct from your income before calculating profit (e.g., equipment, travel, home-working costs).

Making Tax Digital (MTD) – HMRC’s initiative requiring digital record-keeping and software-based tax submissions. Will eventually apply to most self-employed individuals.

Compliance – Meeting HMRC deadlines and tax requirements, including registration, accurate record-keeping, filing returns, and paying tax on time.

Tax Return – The annual form where you report your self-employed income, expenses, and tax owed. Filed through HMRC’s online system or via an accountant.
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