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Filing of Corporation Tax (CT) return amended for your R&D tax credit

Ideally, you will be in the position to file your R&D tax relief claim as part of your original Corporation Tax return, ensuring that you see the financial benefit as quickly as possible. However, it is still possible to file an R&D claim as an amended return.

Not every R&D tax credit provider offers a filing service with HMRC; if not, then you will need to ask your accountant to file the amended return. However, it can be that some accountants are reluctant to file an amended CT return where the information has been provided by a third-party provider.

The right resources for the job

Software is required that allows the presentation of the R&D and Patent Box entries correctly in the CT600 and tax computation. A lot of general accounting software requires workarounds to add the correct entries to the CT600 and tax computation.

To file an amended return, the provider needs a particular understanding of the Corporation Tax rules, as well as R&D and Patent Box rules, to ensure that the return is compliant with any changes to HMRC guidance.

Filing process for an amended CT return

The amended tax computation will need to be sent to the Director or Authorised Signatory along with the final reports for written approval of the amended tax return before submission to HMRC.

Once everything is filed, the amended tax return, tax computation, and submission receipt should be sent to you and your accountant for your records.

Your accountant may need to take this final, amended tax return into consideration when they prepare your tax return for the following period, rather than referring to the original tax return that did not include the R&D.

HMRC’s current processing times

We maintain an internal tracker on the current HMRC processing times, and currently, the average times taken to process claims from the date of submission to receiving cleared funds are:

  • 45 Days for SME R&D credit claims
  • 130 Days for RDEC and hybrid R&D tax credit claims

These are average figures; some claims are processed quicker, and some inevitably take longer.

What information is required to file your R&D tax credit claim?

Gathering the right information in advance will allow prompt submission of the amended return and supporting documents on your behalf, meaning you receive your benefit as quickly as possible.

The full list of requirements can seem surprising to clients, but it is important to remember that you are resubmitting your CT return, so the normal checks and balances will apply.

Here we detail the information that will be required to complete your R&D filing.

Authorisation Contact

This can be a Director or authorised signatory of the company. In cases where it’s not a Director, then a Director needs to provide written confirmation of who they are authorising to sign off the filing documentation on your company’s behalf.

You should provide an email address and contact telephone number for the Authorisation Contact.

The Authorisation Contact needs to provide direct email authorisation to confirm their approval of the documentation to be filed with the R&D claim report. They will also need to be available and contactable to approve the returns.

AML information

The AML information required will always be completed for a current Director of your company.

To complete the AML check, you will need to provide the Directors:

  • Title
  • Full name
  • Personal address
  • Date of birth

Additionally, if the AML contact doesn’t live in the UK, you will need to provide photo identification, either a driver’s licence or passport. If a driver’s license is provided, you will need to provide a photo of the front and back, with all 4 corners included. If a passport is provided, you need to provide a photo of the full back pages of the passport with all 4 corners included

UTR reference

You will need to provide your UTR reference. In cases where the filing is for a group company, or if there is any group relief noted in the tax computation, then you will need to provide the full group UTR rather than the claimant company UTR. You should find this on your tax computations or CT600.

Company Bank Details

Your bank details are required so that HMRC can make the payment directly to your company. This needs to be a UK bank account, with the sort code, account number, account name, and bank name. This needs to be provided on your company letterhead paper.

Final financial statements, tax computations and CT600

You will need to provide copies of your financial statement, tax computations, and CT600, alongside confirmation these have been filed with HMRC.

Reviewed by Samantha Reading, Operations Manager | 10 September 2025

Contact us to find out how you can make the most of your claim