Amending self assessment mistakes after submission

Jun 7, 2024

At John Potter & Harrison, we understand that filing your self assessment tax return can be a stressful experience. Even with the best intentions, mistakes can happen. The good news is that you can amend your return after submission.

This post will guide you through common errors and how to correct them.


Common mistakes in self assessment tax returns

Before we discuss the steps to amend your return, let’s look at some common mistakes people make when filing their self assessment tax returns.


Incorrect income reporting

One of the most common errors is failing to report all sources of income. This might include forgetting to include rental income, freelance work or interest from savings accounts. It’s crucial to ensure all income is accurately reported to avoid penalties.


Miscalculated expenses

Claiming expenses can be tricky, especially if you’re unsure what qualifies as deductible. Mistakes often occur when overestimating or underestimating expenses, leading to incorrect tax calculations.


Wrong personal details

It might seem simple, but errors in personal information such as your name, address or national insurance number can cause significant issues. Double-checking these details before submission can save you a lot of trouble.


Missing deadlines

Filing your return late can result in penalties. According to HMRC, more than 1m taxpayers missed the self assessment deadline in 2023. Keeping track of deadlines and setting reminders can help avoid these costly mistakes.


How to amend your tax return

If you’ve realised there’s a mistake in your submitted self assessment tax return, don’t panic. Here’s how you can amend it.


Online amendments

If you filed your return online, you could correct mistakes easily via the HMRC online service. Here’s a step-by-step guide:

  1. Log in to your HMRC account.
  2. Select the tax year you need to amend.
  3. Click “Amend self assessment return”.
  4. Make the necessary changes.
  5. Save and submit the amended return.


Paper returns

If you filed a paper return, you must download a new tax return, complete the correct sections and send it to HMRC. Be sure to include a cover letter explaining the changes and stating that it’s an amendment to your original return.


Contacting HMRC

If you need assistance or are unsure about the changes, you can contact HMRC directly. They can provide guidance and ensure your amendments are processed correctly.


Important deadlines for amendments

You can change your tax return within 12 months of the original filing deadline. For example, if you filed your 2022/23 tax return by 31 January 2024, you have until 31 January 2025 to make any amendments.


Avoiding future mistakes

Correcting mistakes is essential, but it’s also crucial to avoid them in the first place. Here are some tips to help you file accurate returns in the future.


Keep organised records

Maintain detailed and organised records of all your income and expenses throughout the year. This will make it easier to complete your tax return accurately.


Use accounting software

Consider using accounting software to track your finances. Many tools can integrate with HMRC’s system, reducing the likelihood of errors.


Double-check before submission

Always double-check your return for any errors before submitting it. Reviewing your information can catch simple mistakes that could lead to issues later.


Understanding penalties and interest

If you’ve made a mistake that results in underpaid tax, HMRC may charge interest and penalties. The penalty amount depends on how much tax you owe and the nature of the error. Penalties can range from 0% to 100% of the unpaid tax, depending on whether HMRC believes the error was careless or deliberate.


Help is at hand

Filing your self-assessment tax return accurately is crucial, but mistakes can happen. Amending your return after submission can save you time, money and stress.

At John Potter & Harrison, we’re here to help you navigate the process and ensure your tax affairs are in order. If you’re unsure about any aspect of your tax return, we offer comprehensive self assessment services to ensure your return is accurate and complete.

If you need assistance with your self assessment tax return or have any questions about amendments, don’t hesitate to contact us.

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