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Tax and Compliance

R&D Tax Credit Claim Process: Timeline and Documentation for Agencies

6 min read ·

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JW

Editorial Lead · Published 19 May 2026

Editorial content from the Agency Founder Finance team. For decisions specific to your agency, book a call.

TL;DR

A practical guide to the R&D tax credit claim process for UK agency founders. Covers the timeline from project identification to submission, the documentation you need, and the common mistakes that delay or reject claims.

What is the R&D Tax Credit Claim Process for Agencies?

If your agency develops software, builds complex digital platforms, or solves technical problems through experimentation, you could be eligible for R&D tax credits. The process has changed significantly in the last two years, and getting it wrong means your claim gets rejected.

Here is the timeline and documentation you need, step by step.

Step 1: Identify Qualifying R&D Activity

Before you think about forms, you need to identify which projects qualify. HMRC looks for projects that sought to achieve an advance in science or technology, where the outcome was uncertain, and where you attempted to overcome a technical challenge.

For agencies, qualifying activity often includes:

  • Building custom software platforms where existing solutions did not work
  • Developing algorithms or data processing methods that pushed beyond standard practice
  • Creating integrations between systems that required novel technical work
  • Designing user interfaces for complex data visualisation where the technical approach was uncertain

Routine website builds, standard template customisation, or straightforward app development rarely qualify. The key question is: did your team have to overcome a technical uncertainty that a competent professional in the field could not solve immediately? [1]

Step 2: Gather the Technical Report

HMRC requires a report that explains the R&D project and the qualifying costs. This report should be prepared by a qualified person, such as a chartered accountant or a tax specialist. [1]

The technical report needs to cover:

  • The scientific or technological baseline at the start of the project
  • The technical uncertainty you faced
  • The work undertaken to overcome that uncertainty
  • The advance achieved (or attempted)
  • The qualifying costs incurred

This is not a marketing document. It is a technical explanation written for HMRC inspectors. If your agency built a machine learning tool to automate content tagging, the report needs to explain what was technically uncertain about the approach, not just that it saved time.

Step 3: Calculate Qualifying Costs

For accounting periods beginning on or after 1 April 2023, qualifying costs include cloud computing and data licence costs, but only the portion used for qualifying R&D. [2] This is a significant change for agencies that rely on AWS, Azure, or Google Cloud for development and testing.

Typical qualifying costs for agencies include:

  • Staff salaries and employer NI for employees directly engaged in R&D
  • Externally provided workers (freelancers or contractors) working on qualifying projects
  • Cloud computing costs for development, testing, and deployment environments
  • Data licence fees for datasets used in qualifying R&D
  • Consumables and software licences used directly in the R&D

You need to apportion costs carefully. If a developer spends 60% of their time on qualifying R&D and 40% on routine client work, only 60% of their salary qualifies. HMRC expects clear time records or a reasonable apportionment methodology.

Step 4: Submit the Claim Notification Form (If Required)

For accounting periods beginning on or after 1 April 2023, companies planning to claim R&D tax relief may need to submit a Claim Notification Form. The deadline for submission is linked to your company's period of account and ends six months after. [2]

This is a new requirement. If you miss the notification deadline, you cannot make a claim for that period. Your accountant should handle this, but you need to know it exists. If you are approaching the end of your accounting period, ask your accountant whether you need to file a notification.

Step 5: Complete the Additional Information Form

This is the most critical step. The additional information form must be submitted before or on the same day you submit the Company Tax Return (CT600). [3]

If you send the additional information form and the CT600 on the same day, you must send the form first, followed by the tax return. If the tax return is submitted before the additional information form, the claim will be rejected. [3]

You can complete the additional information form if you are a representative of the company or an agent acting on behalf of the company, using an agent services account. [3] If you are an agent, you must log in to your agent services account before you can complete the form on your client's behalf. [3]

If you do not submit this form, any R&D or expenditure credit claim will not be accepted. [3] That is not a warning. That is the rule.

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For accounting periods beginning on or after 1 April 2024, the additional information form requires additional details for Northern Ireland-based companies: registration details, sector, and de minimis state aid received over the past 3 years. [2]

Step 6: Submit the Company Tax Return (CT600)

The claim must be made in the company's tax return or by an amendment to that return. [1] Your accountant will complete the CT600 and include the R&D claim in the relevant boxes.

The deadline for making an R&D tax credit claim is two years from the end of the accounting period. [1] For example, if your accounting period ends on 31 March 2025, you have until 31 March 2027 to submit the claim. But do not wait that long. HMRC is increasingly scrutinising late claims, and the documentation gets harder to gather the further back you go.

Timeline Summary

Here is the timeline for a typical agency with a 31 March year end:

  • April to June: Identify qualifying projects and gather technical documentation
  • July to September: Calculate qualifying costs and prepare the technical report
  • October to December: Submit the claim notification form (if required)
  • January to March: Complete the additional information form and submit the CT600
  • April to June (following year): HMRC reviews the claim and issues repayment or credit

HMRC typically takes 6 to 12 months to process R&D claims. If your claim is straightforward and well-documented, it may be faster. If HMRC opens an enquiry, it can take 18 months or longer.

Common Pitfalls for Agencies

Claiming for routine work

HMRC sees a lot of claims from digital agencies for standard website builds. If you are not overcoming a technical uncertainty, it is not R&D. Claims that inflate routine work as R&D get rejected, and repeated poor claims can trigger an enquiry into all your future claims.

Poor time records

If you cannot show how much time each employee spent on qualifying R&D, HMRC will challenge the claim. Use timesheets, project management tools, or a clear apportionment methodology. Do not guess.

Missing the additional information form

This is the most common reason claims are rejected. The form must be submitted before the CT600. If your accountant submits the CT600 first, the claim is dead. [3]

Falling for fraudulent "tax credit" schemes

HMRC has issued a new Tax Fraud Warning aimed at employers, recruitment agencies and others involved in the temporary labour market. Organised crime groups are increasingly targeting this sector with payroll models that promise reduced employment costs, often framed as access to 'tax credits' that can be used to lower PAYE and National Insurance Contributions (NIC) liabilities. HMRC is clear that these models are fraudulent. [4]

Employers and agencies who use them can become liable for the full unpaid tax/NIC, penalties, and interest, even if the scheme was promoted by a third-party payroll provider. [4] These schemes claim to acquire businesses, sometimes those in administration, that allegedly hold unused tax credits with HMRC. HMRC reports that in many cases no taxes are being paid at all. [4]

If a promoter offers you access to "tax credits" to reduce your payroll costs, walk away. It is fraud.

How a Specialist Agency Accountant Helps

Working exclusively with agency founders, we handle the entire R&D claim process. We identify qualifying projects, prepare the technical report, calculate costs, submit the additional information form, and file the CT600. We also handle HMRC enquiries if they arise.

If you are considering an R&D claim, start the conversation early. The documentation is easier to gather while the project is still fresh in your team's minds. Waiting until the year end means you will be reconstructing technical work from memory, which leads to weaker claims.

We work with digital agencies, creative agencies, web design agencies, and SEO agencies across the UK. If your agency has done genuinely technical work, we can help you claim what you are entitled to.

For more on how we support agency founders, see our full range of services or get in touch.

Sources

  1. pearsonmay.co.uk: How to make a successful R&D claim - Bath - Pearson May
  2. buzzacott.co.uk: Getting your R&D tax credits claim process right - Buzzacott
  3. gov.uk: Additional information you must submit before you claim Research...
  4. att.org.uk: Safeguard Your Payroll: Don't fall for fake 'Tax Credit' schemes

Frequently asked questions

How long does the R&D tax credit claim process take for an agency?
From project identification to submission, expect 3 to 6 months for a well-prepared claim. HMRC then takes 6 to 12 months to process the claim and issue repayment. If HMRC opens an enquiry, it can take 18 months or longer. Start the process early, ideally before your year end, so you have time to gather proper documentation.
What documentation do I need for an R&D tax credit claim?
You need a technical report explaining the qualifying R&D project, the technical uncertainty, and the advance achieved. You also need cost records showing qualifying expenditure on staff, freelancers, cloud computing, data licences, and consumables. Time records or a clear apportionment methodology are essential. The additional information form must be submitted before the CT600.
Can a marketing agency claim R&D tax credits?
Yes, if the agency has done genuinely technical work that advanced science or technology. Building custom software platforms, developing novel algorithms, or creating complex integrations can qualify. Routine website builds, standard template customisation, and straightforward app development do not qualify. The key test is whether your team overcame a technical uncertainty that a competent professional could not solve immediately.
What happens if I submit the CT600 before the additional information form?
The claim will be rejected. According to gov.uk guidance, the additional information form must be submitted before or on the same day as the Company Tax Return. If submitted on the same day, the form must go first. If the tax return is submitted first, the claim is not accepted. There is no way to fix this after the fact for that accounting period.

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