HMRC Issues Warning About a Common Self Assessment Mistake

HMRC has issued a warning for UK households, asking them to follow strict punctuation rules when filling out their tax returns. The warning follows a case where an individual struggled to enter their business name when registering for Self Assessment.

The incident has prompted HMRC to clarify that certain characters are not permitted in the business name field. The tax authority urged taxpayers to double-check how they enter information, as small errors can delay the registration process.

Punctuation Rules Cause Unexpected Snags

HMRC explained that some punctuation marks will not be accepted when filling in the business name section. In particular, the system does not allow semicolons in descriptions or names. Taxpayers are instead expected to use commas or simpler wording if they need to separate different types of work.

Although this may seem like a minor detail, incorrect punctuation can trigger an error message that prevents the form from being submitted. This can be confusing for those who believe they have followed all the rules, especially if the rejection message is unclear or incomplete.

HMRC also advised taxpayers to re-enter the business name without unnecessary capitalisation if repeated attempts fail. The guidance is part of an effort to reduce avoidable errors when registering for Self Assessment Tax Return and help forms pass through the system smoothly.

What to Do If Your Registration Form Is Rejected

When the form cannot be processed, HMRC encourages individuals to check for characters or formatting that may be causing the issue. In cases where the error message is unclear, the department may ask for a screenshot with sensitive details covered so they can identify what is causing the problem.

These checks are particularly important for new business owners or first-time Self Assessment filers who may be unfamiliar with the technical limits of HMRC’s online forms. Ensuring the correct formatting can save time, prevent delays in registration and reduce the risk of missed deadlines.

If problems persist, HMRC usually provides step-by-step advice based on the specific error message shown on the screen. Most issues can be resolved by adjusting the wording or retyping the information in a simpler format.

Reminder on Who Must Follow Making Tax Digital (MTD)

Alongside the warning, HMRC also reiterated the current position on Making Tax Digital for Income Tax. The upcoming rules will require digital record-keeping and quarterly updates for landlords and sole traders with more than £50,000 in combined gross income from April 2026.

Those earning less than this threshold amount will be brought into the MTD net gradually in 2027 and 2028. However, anyone can choose to take part voluntarily if they prefer the digital approach or want to prepare early for future changes.

Conclusion

HMRC’s reminder highlights how small technical details can create obstacles for taxpayers who are simply trying to register or update their information. Clearer awareness of formatting rules may help people avoid unnecessary setbacks when completing Self Assessment forms.

As the UK gradually moves toward a more digital tax system, understanding these administrative requirements becomes increasingly important. Whether registering for the first time or preparing for upcoming changes, taxpayers may benefit from checking their entries carefully to ensure a smooth process.