How to claim R&D tax relief for the first time: R&D tax credits step-by-step guide

Claiming R&D tax credits for the first time can seem complicated, but with a clear, step-by-step UK guide, the process becomes far more manageable. This guide explains everything you need to know to confidently and compliantly submit an R&D tax credit claim to HMRC.

How do the claimable periods determine whether an R&D tax credit claim is successful?

R&D tax credits are a valuable incentive for UK businesses working on projects and seeking to achieve a scientific or technological advance. If you are preparing to submit an R&D claim, it is vital to ensure that your accounting period complies with HMRC requirements before proceeding. 

Your R&D tax credit claim must relate to the company’s Corporation Tax accounting period, as this determines both which costs can be claimed and when the claim must be submitted.

R&D tax relief claims must be submitted within two years of the end of the relevant Corporation Tax accounting period. Where a company prepares accounts covering more than 12 months, HMRC requires that period to be split into separate Corporation Tax accounting periods. Each accounting period must have its own R&D claim and its own two-year submission deadline.

Ensuring your accounting period meets the R&D claim criteria is essential, as claims submitted outside of these limits may be rejected by HMRC or delayed during review.

For accounting periods beginning before 1 April 2024, companies could claim R&D tax credits under one of two schemes which are called RDEC and SME. The R&D Expenditure Credit (RDEC) was typically used by larger companies, as well as some small and medium-sized enterprises that did not qualify for SME tax relief. The other option was the SME R&D Tax Relief Scheme, which was designed for small and medium-sized enterprises undertaking eligible scientific or technological research and development activities.

Now, for accounting periods beginning on or after 1 April 2024, HMRC introduced new schemes, these are known as the merged scheme and the ERIS scheme. The merged scheme replaces the SME and RDEC schemes for most companies. ERIS applies to R&D-intensive small and medium-sized enterprises and has been designed to provide enhanced support to UK businesses that have spent a high percentage of their expenditure on eligible R&D activities.

It is key that a business selects the correct scheme for their specific accounting period as it will ensure that the research and development relief is processed efficiently and correctly by HMRC.

When does an R&D Claim Notification Form need to be submitted to HMRC?

Submitting an R&D Claim Notification Form is one of the most important steps to consider during the claiming process, especially for businesses claiming R&D tax credits for the first time. 

This type of form must be submitted if this is your first ever R&D tax relief claim or if you are yet to claim for the previous three accounting periods. The R&D Claim Notification Form deadline is six months after the end of the accounting period that the business is claiming for. If the CNF has not been submitted within this timeframe, the R&D tax credit claim will be invalid and not accepted by HMRC.

You may also be wondering when you need to submit a Claim Notification Form, which is also explained in further detail within HMRC’s expert guidance.

How do you identify and calculate qualifying R&D costs?

After confirming the eligibility of your R&D claim and submitting your Claim Notification Form, the next step is to identify your qualifying R&D expenditure. 

Qualifying research and development costs will likely include staff salaries and employer PAYE/NIC contributions for employees that have been involved in R&D, subcontractor and externally provided worker costs, software used directly for R&D purposes and consumables used or transformed during R&D activities.

These R&D costs must be submitted as accurately as possible to R&D activities to avoid the risk of reduced R&D tax relief, a delay in the claiming process, or a potential HMRC enquiry. Referring to an R&D tax credit calculation guide can help solidify the compliancy of your figures, particularly where the PAYE/NIC cap applies.

What documentation is required to submit an R&D claim?

HMRC requires clear evidence to support an R&D tax credit claim. Having the correct documentation ready in a timely manner to submit is paramount to minimise risks during the process. In the event of an enquiry, having HMRC enquiries defence support in place can provide reassurance and expert representation throughout the review process.

For an R&D claim to be classed as compliant and complete, the submitted documentation should include a financial breakdown of your qualifying R&D expenditure, details of the scientific or technological uncertainties faced during the project and how they were resolved, and a technical explanation that outlines the scientific or technological advancement the project aimed to achieve.

To ensure that no critical information has been overlooked, we strongly recommend reviewing a checklist of documents required to submit an R&D claim before progressing to the next stage of the R&D tax credit process. This can be extremely helpful for businesses who are claiming for the first time.

How is an Additional Information Form (AIF) submitted?

An Additional Information Form submission is a mandatory requirement for any R&D tax credit claim and must be correctly submitted before or on the same day as your Corporation Tax return. 

The AIF includes a breakdown of the qualifying costs, descriptions of qualifying R&D projects, confirmation of the R&D scheme that is being claimed and lastly the details of who prepared the claim. The Additional Information Form must be completed prior to the Corporation Tax Return being submitted with the R&D claim. For this reason, referring to an Additional Information Form (AIF) guide before submission is strongly recommended to avoid any risk of rejection.

What is a CT600 and CT600L and how are they submitted?

The final step in the R&D tax claim process is submitting your Corporation Tax return to HMRC. This is where you will see terms such as CT600 and CT600L, but you may be wondering what they mean and how they are submitted. 

The CT600 is your Corporation Tax Return and it must include the R&D claim figures and be supported by the CT600L additional documentation. The CT600L is the supplementary R&D form that supports those figures and provides any additional details. All figures submitted in the CT600, CT600L and Additional Information Form must match exactly as any inconsistencies may lead to delays or an HMRC enquiry.

However, if you are unsure whether your project is eligible to claim, guidance regarding how far back can you claim should clarify your concerns.

Want to claim R&D tax credits for the first time with confidence?

While the claiming process may seem complex at first, but with the right guidance to help you along the way, you can begin your first R&D claim with ease and compliance. 

Understanding which scheme applies to your claim, meeting deadlines, preparing correct documentation and submitting compliant forms can all work hand in hand to allow you to approach the situation with confidence.

In 2026, R&D tax credits remain a valuable incentive for UK businesses to invest in scientific and technological innovation, combining that with preparation, your R&D claim can be submitted accurately and in line with the eligibility criteria set by HMRC.

If you are unsure whether your research qualifies, we recommend that you use the HMRC R&D eligibility tool on the GOV.UK website. Their articles and guides can help you determine whether your project is eligible for R&D tax relief before proceeding with your claim.

For more information regarding claiming R&D tax credits for the first time, please visit our website for further guidance or please do not hesitate to get in touch.