At Godfrey Mansell & Co Accountants, we understand that navigating the intricacies of self-assessment tax returns can be a daunting task. Understanding the most frequent mistakes taxpayers make, is your first line of defence against filing errors. By familiarising yourself with these pitfalls, you can use this knowledge as an essential part of your tax return review checklist for a smooth and compliant tax return and submission to HMRC.
To help you streamline the process, we have compiled a list of common mistakes made during self-assessment and guidance on how to avoid them.
Incorrect Personal Information
Providing incorrect personal information on your self-assessment tax return can lead to a plethora of complications. This includes errors in your name, address, contact details or National Insurance number, which can cause delays in processing and potential penalties. Ensure all personal details are accurate before submission by double-checking your information and verify the information held.
Overlooking Taxable Income Sources such as Income from a Side Hustle
With the rise of gig economy jobs and side hustles, many individuals are earning additional income outside of their primary roles. It is crucial to remember that all sources of income must be included in your self-assessment tax return. Failing to declare income from additional ventures can lead to penalties and interest charges. To avoid this mistake, keep a comprehensive record of all income and expense throughout the year. Consult with our team at Godfrey Mansell Accountants for guidance on reporting side income accurately.
Expense Claim Errors
Another frequent pitfall is making errors in expense claims. Claiming the wrong amount or failing to claim legitimate expenses can have a detrimental impact on your tax liability. Be meticulous in keeping track of your receipts / invoices and documentation throughout the year. Categorising expenses can also simplify the process when it comes time to file. Maintain a detailed record of all business-related expenses to ensure accuracy on your return.
Not Claiming Allowable Expenses
Many Tax Payers fail to claim all allowable expenses, resulting in higher tax liabilities than necessary. Allowable expenses are costs incurred solely for business purposes, and claiming them is crucial for reducing overall profits and tax owed. Some common allowable expenses include office supplies, travel expenses, and professional fees. Maintain a comprehensive list of allowable expenses and periodically review it with your accountant to ensure you are fully leveraging your claims.
Not Utilising Tax Allowances and Tax Relief
The overlooking of valuable tax-free allowances and reliefs and elgibility, these allowances can significantly reduce your taxable income if appropriately claimed. Common examples include:
Personal Allowance (£12,570 for 2025/26 tax year)
Marriage Allowance
Trading Allowance (£1,000 for self-employment)
Property Allowance (£1,000 for rental income)
Pension contributions relief
Charitable donation relief through Gift Aid
It is essential to stay informed about the various reliefs available and by consulting with an accountant , they can help you identify and maximise these opportunities.
Missing Something Off Your Tax Return
Completing a self-assessment tax return can be overwhelming, and it is not uncommon to inadvertently overlook certain details. Missing income or expenses can lead to inaccurate filings and possible penalties. To mitigate this risk, create a checklist of all items that need to be included in your tax return. Carefully review your previous tax returns and verify all information to ensure nothing is omitted..
Missing the Deadline
One of the most prevalent errors when completing self-assessment tax returns is missing the deadline. The consequences can be significant, resulting in late filing penalties and interest charges that can quickly accumulate. As a general rule, tax returns must be submitted by 31 January following the end of the tax year. To avoid this mistake, ensure you are well-prepared in advance. Set reminders well before the deadline, and if necessary, consider using accounting software or consulting with an accountant to stay organised.
Missing Payments on Account
Missing payments on account can be a significant issue. Payments on account are advance payments towards your tax bill for the following year, and failing to make these payments can lead to penalties and interest. To avoid confusion, set reminders for these payments, which are typically due on 31 January and 31 July. Consult with our knowledgeable team at Godfrey Mansell & Co Accountants for tailored advice regarding payments on account and ensuring timely submission.
Conclusion
Completing a self-assessment tax return does not have to be a stressful undertaking. By understanding these common mistakes and implementing preventative measures, you can ensure a smoother filing process and avoid unnecessary penalties. At Godfrey Mansell & Co Accountants, we are committed to providing comprehensive accounting and tax advisory services tailored to your needs in Birmingham, Worcester, and the West Midlands and beyond. Should you need assistance or have any questions regarding your self-assessment tax return, please do not hesitate to get in touch with our experienced team.
Share this post: