When and How to Amend Your Company Tax Return

Introduction

If you've spotted an error on your Company Tax Return after filing it, you may need to amend it to avoid HMRC opening an enquiry. The process for making corrections depends on when you filed and what type of error you've made, but in most situations you can amend your return online or by writing to HMRC.

Why you might need to amend your return

There are several reasons you might need to amend a Company Tax Return you've already submitted:

Errors in your figures – You may have discovered mistakes in your profit calculations, capital allowances claims, or tax computations after filing.

Changes in legislation – Past legislative changes have sometimes required companies to amend returns that were filed before new rules received Royal Assent but covered accounting periods after the rules took effect.

Missing information – You might have filed without certain details and need to add them later.

Reliefs or elections – You may want to claim a relief you didn't include originally, or make a tax election you missed.

It's important to amend your return as soon as you realise something is wrong. HMRC may open an enquiry into your return if they spot inconsistencies and you haven't corrected them promptly.

Specific legislative changes from 2017

Following the Finance (No 2) Act 2017, some Company Tax Returns became incorrect even though they were filed in good faith. The Act received Royal Assent on 16 November 2017, but many of its provisions applied retrospectively.

You need to amend your return if you filed before 16 November 2017 and your accounting period ended after:

8 March 2017 – if your return contains entries affected by assets appropriated to trading stock

1 April 2017 – if your return contains entries affected by:

• Loss reform
• Corporate interest restrictions
• Substantial shareholdings exemption
• Offshore property developers
• Restrictions to deductions for employers' payments into employee benefit schemes

These specific circumstances are now historical, but they illustrate how legislative changes can require amendments to returns that were technically correct when filed.

How to amend your Company Tax Return

There are two ways to amend your return:

Online amendment

You can sign in to HMRC's online services and amend your return digitally. This is the quickest method and means your amendment will be processed faster.

To amend online, sign in through your Government Gateway account using the same credentials you used to file the original return.

Written amendment

Alternatively, you can write to your company's Corporation Tax office. You'll find this address on recent tax forms or letters you've received from HMRC.

In your letter, include:

• Your company name and registration number
• Your Corporation Tax reference (UTR)
• The accounting period you're amending
• Clear details of what you're correcting and why
• The corrected figures

If you don't have your Corporation Tax office address, you can call the Corporation Tax helpline to obtain it.

When to amend your return

The sooner you amend an incorrect return, the better. While there are time limits for making amendments (you can amend a return within 12 months of the filing deadline in normal circumstances), you shouldn't wait.

HMRC expects you to take reasonable care with your tax affairs. If they discover errors before you correct them, they may:

• Open a formal enquiry into your return
• Charge penalties if they believe the error was careless or deliberate
• Assess additional tax with interest

By amending your return promptly when you discover an error, you demonstrate that you're acting responsibly and reduce the risk of penalties.

Getting help with amendments

If you need assistance with specific technical areas, HMRC provides dedicated support:

For loss reform queries – Email ct.lossreform@hmrc.gov.uk

For corporate interest restriction queries – Email interest-restriction.mailbox@hmrc.gov.uk

For other questions – Contact your company's HMRC Customer Relationship Manager (CRM) if you have one. If your company doesn't have a CRM, contact the Corporation Tax helpline.

Your accountant can also help you determine whether an amendment is necessary and ensure it's completed correctly.

What happens after you amend

Once you've submitted your amendment:

• HMRC will process the change and update their records
• If the amendment results in additional tax due, you'll need to pay the extra amount (with interest from the original due date)
• If you've overpaid, HMRC will refund the difference with interest
• HMRC may contact you if they have questions about your amendment

Keep records of what you amended and why. If HMRC does open an enquiry, having clear documentation of the error and correction will help resolve matters quickly.

Sources

• Corporation Tax: check if you must amend your Company Tax Return

This article provides general guidance based on current HMRC rules. For advice specific to your situation, speak to your accountant.