R&D Tax Credit Checklist 2026: 10 Essential Steps for a Compliant Claim

Claiming R&D tax relief in 2026 looks very different from even two years ago. The merged scheme is now the default, the Claim Notification Form is mandatory for many companies, and HMRC enquiry rates remain elevated. Here's the up-to-date 10-step process to get your claim through cleanly.

• Identify qualifying projects — focus on activities aimed at resolving scientific or technological uncertainty
• Submit the Claim Notification Form (CNF) — mandatory for first-time claimants or those who haven't claimed in 3 years. Do this early.
• Confirm your company's eligibility — UK Corporation Tax payer with eligible R&D spend in the accounting period
• Choose the correct scheme — merged scheme or ERIS (the legacy SME and RDEC schemes have closed for new accounting periods)
• Compile eligible costs — staff, subcontractors, consumables, software, cloud, and data
• Gather supporting evidence — contemporaneous technical and financial records, and start answering the AIF questions as you go
• Estimate your claim size — apply the merged scheme 20% credit or ERIS 86% uplift + 14.5% repayable credit
• Review for compliance risks — overseas spend, contracted-out R&D, scheme eligibility
• Prepare and submit the Additional Information Form (AIF) — finalise project descriptions and cost breakdowns in HMRC's online form
• Complete your Company Tax Return (CT600) — include the CT600L for R&D claims

Understanding Eligibility

To determine if your company qualifies for R&D tax relief, you'll need to align your activities with HMRC's criteria. Once that's clear, the next step is identifying which of your projects meet the requirements for qualifying R&D activities.

Qualifying R&D Activities

To qualify, your projects must address scientific or technological uncertainties that a competent professional in the field cannot easily resolve. This requires a structured, investigative approach.

Examples of qualifying activities include creating new production methods, developing innovative drugs, or designing cutting-edge software algorithms. Even service-based projects may qualify if they involve genuine technological progress, such as advanced route optimisation tools or unique risk assessment models. For a fuller breakdown by sector, see our guide on what work qualifies for R&D tax relief with examples.

However, some activities are excluded. These include market research, routine data collection, standard commercial production of existing products, and tasks where the necessary scientific or technological knowledge is already available to professionals in the field.

Company Requirements

To claim R&D tax relief, your company must be subject to UK Corporation Tax and have eligible R&D expenses. The claim must come from the entity that either carried out the R&D work or contracted it. Under the merged scheme rules for accounting periods starting on or after 1 April 2024, the rules on who can claim for contracted-out R&D have tightened — see Step 8 below.

You should maintain thorough records of your technical work and associated costs. HMRC may require evidence showing the advancements pursued, the uncertainties tackled, and the systematic methods used.

Merged Scheme vs ERIS

For accounting periods beginning on or after 1 April 2024, the legacy SME and RDEC schemes have been replaced by:

• The merged R&D expenditure credit scheme — the default scheme for most claimants, regardless of company size
• Enhanced R&D Intensive Support (ERIS) — a higher-rate alternative available only to loss-making SMEs whose R&D expenditure is at least 30% of total expenditure

If your accounting period began before 1 April 2024, the old SME and RDEC rules still apply to that period — but most accounting periods you're claiming for now will fall under the new regime.

The 10 Steps

Following these ten steps can help you prepare and submit a well-documented R&D tax relief claim that aligns with HMRC's guidelines while maximising your potential relief.

Step 1: Identify Qualifying R&D Projects

Start by reviewing your activities to pinpoint projects that aimed to advance science or technology. Focus on work where your team faced genuine uncertainties that couldn't be solved using existing knowledge in your field.

To qualify, projects must meet HMRC's BIS Guidelines on the Meaning of R&D for Tax Purposes — the official definition HMRC uses to assess every claim. If your project doesn't fit the BIS criteria, it doesn't qualify, no matter how innovative it looked internally.

Document these projects with a short narrative covering the uncertainties, methods, and outcomes. For example, in software development, this could involve creating new algorithms or tackling complex integration issues. In manufacturing, it might mean developing new materials or improving production methods.

Don't overlook failed projects — these can still qualify if they involved genuine efforts to make technological progress. The main requirement is proving that competent professionals in your field couldn't have easily determined the solution at the start.

Step 2: Submit the Claim Notification Form (CNF)

If you think you may have a claim, submit the Claim Notification Form (CNF) as early as possible. The CNF is a pre-notification you file separately from the claim itself, and missing the deadline is the single most common irreversible mistake under the post-2023 regime.

You must submit a CNF for an accounting period if either applies:

• You are a first-time R&D claimant, or
• Your most recent claim was submitted more than three years before the last day of your claim notification period

The deadline is six months after the end of the accounting period. For a December 2025 year-end, that's 30 June 2026. Miss it and your claim is invalid — HMRC will reject it automatically, with no appeal.

Even if you're not certain you'll claim, file the CNF if there's a reasonable chance. There's no downside to filing one and not following through with a claim, but there's no remedy for filing late. See our R&D pre-notification guide for full eligibility rules and exceptions.

Step 3: Confirm Company Eligibility

Ensure your company meets the basic criteria for claiming R&D tax relief. Your business must:

• Be liable for UK Corporation Tax
• Have incurred qualifying R&D expenses during the relevant accounting period

Your company must either have conducted the R&D work directly or paid for it to be done on your behalf. Check that your accounting records are complete and accurate, as HMRC may request detailed cost breakdowns. If you're part of a group, confirm which entity incurred the expenses and has the right to claim.

Step 4: Determine Applicable Scheme (Merged Scheme or ERIS)

For accounting periods starting on or after 1 April 2024, you'll claim under either the merged scheme or ERIS.

ERIS is available only if all of the following apply:

• You are an SME (under 500 staff, turnover under €100m, balance sheet under €86m)
• You are loss-making (or the claim itself turns you loss-making)
• Your R&D expenditure is at least 30% of your total expenditure for the period

If you fail any of those tests, you'll claim under the merged scheme.

The merged scheme applies to companies of all sizes — large companies, profitable SMEs, and loss-making SMEs that don't hit the 30% intensity threshold all use it. The mechanics are based on the old RDEC scheme: an above-the-line taxable credit. For a deeper breakdown of how the two regimes interact, see merged RDEC and ERIS rules explained.

Step 5: Compile Eligible Expenditure

List all qualifying expenses. Key categories include:

• Staff costs: Salaries, employer National Insurance, and pension contributions for employees directly involved in R&D
• Subcontractor payments: The rules changed materially from 1 April 2024 — see Step 8. As a starting point, payments to unconnected subcontractors are restricted to 65% of the payment
• Consumable materials: Items used directly in R&D projects qualify, but capital equipment generally doesn't — unless it falls under specific software or data-related categories
• Cloud computing, data licences, and software: All now qualifying since the 2023 reforms, where directly used in R&D activities

Exclude costs related to market research and routine testing.

Step 6: Gather Supporting Documentation (and Start Drafting Your AIF Answers)

Compile evidence to substantiate your claim. This includes:

• Technical narratives: Describe the challenges, methods, and outcomes for each qualifying project
• Project records: Design specifications, test results, research notes, meeting minutes, and email discussions about problem-solving
• Financial records: Link costs to specific R&D activities, using timesheets, invoices, and accounting records
• Baseline evidence: Provide materials like academic papers or industry reports to show the uncertainties weren't solvable with existing knowledge

As you collect this evidence, start drafting your answers to the questions you'll later submit on the Additional Information Form (AIF). HMRC requires you to answer, for each R&D project:

• What is the main field of science or technology the project relates to?
• What was the baseline level of science or technology that the company planned to advance?
• What advance in that scientific or technological knowledge did the company aim to achieve?
• What scientific or technological uncertainty did the company have to overcome?
• How was that uncertainty overcome — what work was done, by whom, and over what period?

Drafting these answers while the work is fresh — rather than reconstructing them at the year-end — produces sharper, more defensible narratives and saves significant time later.

Step 7: Estimate Your Claim Size

Apply the rates that match your scheme:

• Merged scheme: a 20% above-the-line taxable credit on your qualifying R&D expenditure. After corporation tax, the net benefit is roughly 15–16.2p per £1 spent, depending on your CT rate.
• ERIS: your qualifying expenditure is uplifted by 86%, and you can surrender losses for a 14.5% repayable credit on the enhanced figure. Effective benefit: roughly 26.97p per £1 spent.

For staff costs, calculate the percentage of time employees spent on R&D and apply this to their total employment costs. Ensure your estimates are realistic and supported by evidence.

Step 8: Review for Compliance Risks

Before you submit anything, work through the common compliance risks. Spotting issues now is far cheaper than answering an HMRC compliance check later.

• Overseas expenditure: Since 1 April 2024, overseas R&D is only allowable where geographic, environmental, social, or regulatory conditions make it impossible to undertake the work in the UK. Cost or workforce availability are not valid reasons.
• Contracted-out R&D: Under the merged scheme, the customer generally claims for R&D they paid a contractor to undertake — not the contractor. There are exceptions where the contractor is treated as the claimant (e.g. when the customer is overseas or not in scope). Get this wrong and you'll either double-claim or miss the relief entirely.
• Subcontractor 65% restriction: Still applies in specific situations under the merged scheme — confirm whether the payment falls within the rule before applying it.
• Scheme eligibility: Double-check your ERIS qualification, especially the 30% R&D intensity threshold.

Once you've worked through these, you're ready to submit the AIF.

Step 9: Submit the Additional Information Form (AIF)

The Additional Information Form is mandatory for every R&D claim filed on or after 8 August 2023, and it must be submitted before you file your Company Tax Return — not at the same time.

By this point, the bulk of the work is done. You've drafted the project narratives in Step 6 and have the cost breakdown from Step 5. Submitting the AIF is largely a case of finalising those answers and entering them into the HMRC online form, which guides you through the process.

You'll need:

• Your project narratives — the answers from Step 6, refined
• The cost of each project, broken down by cost category (staff, subcontractors, EPWs, consumables, software, cloud, etc.)
• Confirmation of whether any costs are Qualifying Indirect Activities (QIA) — supporting activities that don't directly resolve uncertainty but contribute to the R&D project. Examples include training staff for the R&D, recruitment for R&D roles, and admin or maintenance work specifically supporting the R&D project. QIA costs qualify, but the form asks you to flag them separately.

Step 10: Complete the Company Tax Return (CT600)

Incorporate your R&D claim into the Corporation Tax return. Under both the merged scheme and ERIS, you'll need the CT600L supplementary form alongside the main CT600.

Ensure all figures match between your Additional Information Form and tax return entries. Discrepancies are one of the most common triggers for HMRC enquiries. Once submitted, see our guide to HMRC R&D claim processing times in 2026 for what to expect next.

If claiming a payable credit under ERIS, complete the relevant CT600L sections to initiate payment. For merged scheme credits, the credit flows through a seven-step waterfall — settling CT first, then PAYE/NIC caps, with any balance payable in cash.

When You Need to Submit Your R&D Claim By

R&D claims must be filed within two years of the end of the accounting period to which they relate. Miss the deadline and the relief is lost — there's no extension mechanism.

And don't forget that the CNF deadline (Step 2, six months after the AP end) sits inside this window. If you haven't filed the CNF on time, the two-year claim window doesn't save you — the claim is invalid before you even get there.

Compliance and Best Practices

With HMRC ramping up its scrutiny of R&D claims, maintaining strong compliance is no longer optional — it's a necessity.

Keeping Detailed Records

When it comes to R&D claims, meticulous record-keeping is your strongest ally.

"Contemporaneous technical and financial documentation isn't legally mandated for R&D claims, but in practice it's what separates a smooth claim from a painful enquiry. Build the records as the work happens, not at year-end." — Adam Park, Founder, Zest Tax.

Set up dedicated project files that include everything from design specifications and test results to research notes and meeting minutes. Don't forget to document technical challenges, attempted solutions, and outcomes — even failed experiments can serve as valid evidence.

On the financial side, detailed timesheets are useful. They should clearly show how employees split their time between R&D and non-qualifying activities. Invoices and purchase orders should be tied directly to specific projects, especially for items like consumable materials and subcontractor payments.

Collaborating with Specialists

Navigating the complexity of R&D tax relief rules — particularly under the new merged scheme — is no small task. Specialists like Zest Tax can help you identify qualifying activities and ensure your records are up to HMRC standards.

Specialists don't just provide guidance — they offer an extra layer of quality assurance. They review technical narratives for clarity, double-check cost calculations, and make sure your documentation aligns with HMRC's expectations.

Steering Clear of Common Compliance Issues

The good news? Compliance efforts are paying off. The error and fraud rate for R&D claims fell from 17.6% in 2021–22 to 5.9% in 2024–25.

"The direction is clear: HMRC's approach to R&D tax relief is becoming more stringent, transparent, and strategically focused." — HMRC.

Common Pitfalls and How to Avoid Them

Misidentifying Qualifying Activities

One of the most frequent mistakes businesses make is claiming activities that fail to meet HMRC's strict R&D criteria. Routine tasks like software updates, incremental product improvements, or market research simply don't qualify.

HMRC focuses on activities aimed at resolving scientific or technological uncertainties. To qualify, you must show that your project tackled challenges that couldn't be solved by a competent professional in the field. For instance, developing a standard e-commerce site using existing frameworks won't count, but creating a cutting-edge algorithm to handle complex data processing might.

Incomplete Documentation

Submitting incomplete or insufficient evidence can invite scrutiny and delay your claim. A common issue is missing contemporaneous records — evidence created during the R&D process rather than reconstructed after the fact. HMRC wants to see detailed project notes, test results, design drafts, and meeting minutes that were documented as the work progressed.

Missing the CNF Deadline

The single most common irreversible mistake in the post-2023 regime. The CNF is a hard, automated cutoff — file it late and the claim is gone. If your accounting period ended in the last six months and you haven't yet checked whether you need a CNF, stop and check now.

Missing Submission Deadlines

HMRC enforces a strict two-year deadline for the claim itself, and missing it means losing your entire claim, no matter how much qualifying expenditure you've incurred.

Conclusion

Claiming R&D tax relief successfully hinges on careful planning and strict adherence to HMRC's guidelines. The ten steps outlined in this checklist offer a clear roadmap to help you maximise your claim while steering clear of common mistakes that could jeopardise the process.

The 2024 merged-scheme reforms have simplified some things (one scheme, one rate for most claimants) and complicated others (contracted-out R&D, overseas expenditure, the CNF pre-notification). The fundamentals — qualifying activities, contemporaneous evidence, accurate costing — are unchanged.

Partnering with experienced R&D tax specialists can make all the difference. Zest Tax offers expert guidance throughout the process, from initial assessment to submission.

Frequently Asked Questions

What criteria must my company's R&D activities meet to qualify for tax relief under HMRC guidelines?

To meet HMRC's criteria for R&D tax relief, your project must aim for an advance in science or technology that contributes to the broader field, rather than just serving your business interests — which means tackling a scientific or technological uncertainty that cannot be easily solved by an expert relying on current knowledge or established methods, and resolving that uncertainty through experimentation that leads to new knowledge or innovative solutions. The work must focus on developing or improving a product, process, or service in a way that goes beyond routine updates or minor tweaks.

What documents do I need to prepare for an R&D tax relief claim, and how should I organise them?

There is no specific minimum standard for record keeping during R&D projects beyond the standards that apply to your business's financial records generally — contemporaneous R&D records aren't legally mandated, just advisable, but robust record-keeping makes HMRC compliance checks significantly more straightforward. The records most claimants find useful are technical project notes (challenges encountered, methods tried, outcomes), financial records linking specific costs to specific R&D activities (invoices, timesheets, payroll data), and supporting evidence showing the baseline state of the field at the time the work was undertaken. Build these records as part of your normal project management rather than reconstructing them after the fact, and you'll be in a far stronger position if HMRC opens an enquiry — and the AIF itself will be much easier to complete.

What's the difference between the merged scheme and ERIS, and which one applies to my business?

For accounting periods beginning on or after 1 April 2024, the UK has two R&D tax relief regimes: the merged scheme is a single 20% above-the-line credit available to companies of all sizes, and is the default that most claimants use; ERIS (Enhanced R&D Intensive Support) is a higher-rate scheme available only to loss-making SMEs whose R&D expenditure is at least 30% of total expenditure. If your accounting period started before 1 April 2024, the legacy SME and RDEC schemes still apply to that specific period.