Submitting your Self Assessment Tax Return might seem straightforward, especially with online accounting software and HMRC’s digital filing system. However, many East London taxpayers are surprised to discover that their returns are delayed, queried, or rejected because of avoidable mistakes.
A rejected or incorrect return does not always lead to immediate penalties, but it can result in processing delays, HMRC enquiries, additional tax liabilities, and unnecessary stress. Understanding why returns fail HMRC’s validation checks is the first step towards avoiding costly errors. At MSCO Accountants, taxpayers are encouraged to review their returns carefully before submission to minimise errors and ensure HMRC compliance.
Incorrect Personal Information Is More Common Than You Think
One of the simplest yet most frequent reasons for rejected Self Assessment Tax Returns is incorrect personal information.
HMRC matches every submission against its records. Even minor inconsistencies can cause validation issues.
Common mistakes include:
- Incorrect Unique Taxpayer Reference (UTR)
- Wrong National Insurance number
- Outdated address details
- Incorrect date of birth
- Misspelled names
Before submitting your return, always ensure your personal details match the information held by HMRC.
Declaring the Wrong Income Sources
Many taxpayers believe they only need to report their primary source of income.
In reality, HMRC expects you to declare all taxable income received during the tax year.
Income often forgotten includes:
- Freelance earnings
- Rental income
- Foreign income
- Dividends
- Interest exceeding allowances
- Side business income
- Capital gains, where applicable
Missing income does not just increase the risk of rejection. It may also trigger an HMRC compliance check.
Claiming Expenses That HMRC Does Not Allow
One of the biggest mistakes made by self-employed individuals is misunderstanding allowable business expenses.
Many taxpayers accidentally include personal costs alongside legitimate business expenses.
Examples include:
- Family holidays recorded as business travel
- Personal mobile phone costs
- Everyday clothing
- Non-business meals
- Personal subscriptions
Only expenses incurred wholly and exclusively for business purposes are generally allowable. Seeking guidance from experienced professionals such as MSCO Accountants can help ensure expenses are claimed correctly while remaining compliant with HMRC rules.
Poor Record Keeping Creates Filing Errors
Many filing mistakes originate months before the return is prepared.
Missing invoices, incomplete receipts, duplicated transactions, and inaccurate bookkeeping often result in incorrect figures being submitted.
Good record keeping throughout the year makes preparing an accurate Self Assessment significantly easier and reduces the likelihood of HMRC queries.
Missing Supplementary Pages
A Self Assessment Tax Return is not always limited to the main return.
Depending on your circumstances, additional pages may be required.
These may include:
- Self-employment pages
- Property income pages
- Partnership income
- Capital Gains pages
- Foreign income sections
Leaving out required supplementary pages can result in an incomplete submission that HMRC may reject or question.
Mathematical Errors Still Happen
Although many online systems perform automatic calculations, manual adjustments and incorrect data entry can still create discrepancies.
Examples include:
- Transposed figures
- Extra zeros
- Decimal point errors
- Incorrect loss calculations
- Misreported tax already paid
Taking time to review every figure before submission can prevent unnecessary delays.
Filing at the Last Minute Increases Mistakes
Many East London taxpayers leave their Self Assessment until the January deadline.
Under pressure, they rush through the return without reviewing supporting records.
This often leads to:
- Missing information
- Incorrect income declarations
- Forgotten expenses
- Late amendments
- Increased risk of penalties if filing deadlines are missed
Preparing your records well before the deadline gives you time to identify and correct errors before submission.
How to Reduce the Risk of HMRC Rejecting Your Tax Return
Before filing your Self Assessment, ask yourself:
- Have I declared every source of income?
- Are my personal details correct?
- Do my figures match my records?
- Have I claimed only allowable expenses?
- Have I completed all required supplementary pages?
- Have I reviewed my return before submitting?
If you are unsure about any answer, professional advice could prevent costly mistakes. MSCO Accountants helps individuals and business owners review their Self Assessment Tax Returns before submission, reducing the risk of avoidable errors and delays.
Conclusion
Submitting an accurate Self Assessment Tax Return is about more than meeting a deadline. It helps you avoid unnecessary HMRC enquiries, processing delays, penalties, and additional tax liabilities. By keeping accurate records, reporting all sources of income, claiming only legitimate expenses, and reviewing your return carefully before filing, you can significantly reduce the likelihood of errors. If you are unsure about any part of your return, working with experienced professionals like MSCO Accountants can provide peace of mind and help ensure your submission is accurate, compliant, and completed on time.
Frequently Asked Questions
Can HMRC reject a Self Assessment Tax Return?
Yes. Returns may be rejected due to validation errors, missing information, incorrect personal details, or incomplete sections. HMRC may also open enquiries if inaccuracies are identified after submission.
What happens if I submit incorrect information?
You should correct the error as soon as possible. Depending on the nature of the mistake, HMRC may require an amendment and could charge penalties if inaccuracies are careless or deliberate.
How long do I have to amend a Self Assessment Tax Return?
Most Self Assessment returns can be amended within the timeframe permitted by HMRC after the filing deadline.
Can an accountant help if my return has already been submitted?
Yes. An accountant can review your return, identify errors, submit amendments where appropriate, and communicate with HMRC if necessary.
Is online filing safer than paper filing?
Online filing includes automated validation checks that reduce calculation errors, but accurate information and supporting records remain essential.
