HMRC Warns Against Punctuation Errors In Self‑assessment Forms

HM Revenue & Customs (HMRC) recently reminded taxpayers to be careful when entering business names in self‑assessment forms. A social media enquiry prompted the alert. HMRC said that even small punctuation errors in self-assessment forms can prevent a it from being accepted. In the exchange, officials explained that semi‑colons are not allowed and advised taxpayers to use commas instead. They also suggested re‑entering business names in lower‑case letters when the system rejects a name.

Why does this matter? 

Digital tax returns rely on strict input rules. Using an illegal character will trigger an error, delay registration and add stress. We understand how easy it is to overlook these minor details and how costly the consequences can be. Below we outline what you need to know and how to avoid common mistakes.

Why accurate self‑assessment submissions are important

The UK’s self‑assessment regime requires millions of people to file returns each year. HMRC warns taxpayers that even small mistakes can delay processing. Mistakes often occur when entering business names. The portal rejects names containing restricted characters – semi‑colons are the most common culprit. For accurate self-assement submissions taxpayers should:

• Stick to permitted punctuation. Use commas instead of semi‑colons.
• Avoid excessive capital letters. Re‑enter the name using lower‑case letters if the system rejects it.
• Keep the business name simple; do not add descriptors or tags that are not part of the registered name.
  
• Remove other special characters (such as ampersands or slashes) unless they appear in the official business name.
• Take a screenshot of any error message and share it with HMRC support if you need assistance.

These simple steps can prevent the frustration of a rejected form.

Making Tax Digital – who needs to comply?

Making Tax Digital (MTD) is the government’s move to digital record‑keeping and quarterly reporting. You must use MTD for Income Tax if you are a sole trader or landlord registered for self‑assessment and your qualifying income is more than £20,000. The rules phase in based on income:

• Income over £50,000 (2024/25 tax year): you must start using MTD from 6 April 2026.
  
• Income over £30,000 (2025/26 tax year): you must start from 6 April 2027.
  
• Income over £20,000 (2026/27 tax year): the government plans to lower the threshold to this level.

If your qualifying income is £20,000 or less, you do not need to use MTD. People who are digitally excluded or meet certain exemptions do not have to sign up. You can choose to join voluntarily if you wish to manage digital tax filing in the UK.

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Key dates for MTD

The MTD timeline includes several important deadlines:

• 31 January 2026: last day to submit your 2024/25 self‑assessment return.
• 6 April 2026: start keeping records using MTD‑compatible software.
• 7 August 2026 and quarterly thereafter: first and subsequent quarterly updates.
• 31 January 2027: final date to submit your 2025/26 return under the old system.

To avoid penalties, ensure you understand when you need to start and that your software is compatible.

Self‑assessment deadlines and registration

Filing on time avoids penalties and interest. Key dates for the 2024/25 tax year include:

• 5 October 2025: deadline to tell HMRC that you need to complete a return if you have not sent one before.
• 31 October 2025: deadline for paper returns.
• 30 December 2025: deadline if you want HMRC to collect tax through your PAYE tax code.
• 31 January 2026: deadline for online returns and for paying any tax owed.
• 31 July (annually): due date for the second payment on account.

If you register after 5 October, HMRC will give you a different filing deadline, but you still need to pay tax owed by 31 January. Early and accurate tax filing reduces stress and gives you time to budget for your bill.

Avoid common errors in self-assessment forms 

Many taxpayers make avoidable errors. The most frequent mistakes include:

• Missing deadlines: Procrastination can result in penalties. Mark deadlines in your calendar and set reminders.
  
• Not applying for a Unique Taxpayer Reference (UTR) early enough: It can take weeks to receive a UTR. Apply well before your first return.
  
• Forgetting tax reliefs and allowances: Keep a record of all claimable expenses, including business costs and charitable donations.
  
• Overlooking payments on account: You may need to pay this year’s bill plus a ‘payment on account’ – 50% of the next year’s liability – in January and July.
  
• Using the wrong tax code: An incorrect code can lead to over- or under-payment. Check your tax code and contact HMRC if there is a mistake.
  
• Failing to declare all income: If you have employment income alongside self‑employment income, use your P60 and P11D to report salary and benefits.
  

By keeping accurate records and double‑checking figures, you can avoid these common traps.

How We Can Help You With Accurate Tax Filing

At Apex Accountants, we specialise in helping individuals and businesses with digital tax filing in the UK. Our team offers:

• Self‑assessment preparation: We collect and review your income and expense records, calculate your tax liability and file returns on your behalf.
  
• Making Tax Digital support: We can set up compatible software, train you on digital record‑keeping and ensure you meet quarterly update deadlines.
  
• Business name and registration guidance: If your business name is rejected, we help you identify the problem and submit compliant details.
  
• Tax planning and relief claims: We identify allowable expenses and reliefs to legitimately reduce your tax bill.
  
• Ongoing advisory services: From payment plans to compliance checks, we provide year‑round support tailored to your situation.

Conclusion

HMRC’s warning about punctuation shows how small details can affect your tax return. Always use commas instead of semicolons and keep business names simple. With new digital reporting rules on the horizon, understanding Making Tax Digital and meeting self‑assessment deadlines is more important than ever. Avoid common mistakes by keeping good records, claiming available reliefs and registering on time. If you need guidance, Apex Accountants is here to help you meet your obligations and minimise tax stress.

FAQs

Why won’t HMRC accept my business name? 

The self‑assessment portal rejects names containing forbidden characters. Semicolons are not allowed – use commas instead. Make sure the name matches your official business name and remove unnecessary capital letters.

When do I need to register for self‑assessment? 

If you have income that isn’t taxed at source (such as trading profits or rental income), you must register by 5 October following the end of the tax year. Doing it early ensures you receive your Unique Taxpayer Reference in time.

Can I still file on paper? 

Yes. HMRC must receive paper returns by 31 October 2025. Online filing is available until 31 January 2026.

Does Making Tax Digital apply to me? 

MTD currently applies only to sole traders and landlords with qualifying income above £50,000 from 2024/25, dropping to £30,000 in 2025/26 and £20,000 in 2026/27. If your income is lower, you can volunteer to sign up but are not obliged to.

What happens if I miss the deadline? 

Late filing penalties start at £100 and increase the longer you delay. Late payment interest and daily penalties can add up. Contact HMRC as soon as possible if you cannot pay on time.

What punctuation can I use in business names? 

HMRC’s style guidance discourages semicolons because they are often misread. The self‑assessment system mirrors this by rejecting semicolons. Use commas or hyphens and avoid other special characters.