Embedded Files
RDEC Calculations:
The 2026 Practitioner’s View:
It is 2026 and you might expect the dust to have fully settled on the post-April 2024 RDEC claims process. The unified scheme has been in place for some time and yet across the industry, a persistent issue remains: incorrectly submitted Research and Development Expenditure Credits (RDEC) tax returns.
The problem I’m addressing here is not the identification of qualifying expenditure—it’s the correct application of the statutory seven-step RDEC claim calculation and its clear presentation in the claimant company’s tax computation.
Except where the claim results in a simple Corporation Tax offset, it is crucial not only to perform the seven steps accurately—since they determine the actual payable tax credit—but also to document them in the tax computation accompanying the CT600 tax return. In our experience, some tax software cannot do this, which can result in the tax return being rejected or delayed, which can be fatal if you've pushed up to the R&D claim filing deadline. This is not optional sequencing—it is a fundamental compliance issue.
Navigating the 7 Steps to Claim Payable RDEC Incentives: A Guide to the Tax Computation
To arrive at the correct payable credit, the RDEC must pass through the following steps in order:
Step 1: Initial Offset Against Corporation Tax
The RDEC, which is worked out at 20% of qualifying R&D expenditure in the period, is first used to off-set any Corporation Tax liability for that same accounting period.
Step 2: Notional Tax Charge
A notional Corporation Tax charge is applied to the RDEC (reflecting its taxable nature). This reduces the effective credit available for further use.
If the RDEC after notional Tax is less than the amount remaining after Step 1, that amount is carried forward to the next accounting period.
Any amount remaining after Step 1, that has not been carried forward, progresses through to Step 3.
Step 3: PAYE/NIC Cap
The payable element of the credit is capped at:
£20,000 plus
300% of relevant PAYE and NIC liabilities (for all staff, not just R&D staff) paid by the company
This cap applies only to any payable element remaining after all tax liabilities have been offset, not the total credit. Any excess above the cap is carried forward to the next accounting period, the remainder goes through to Step 4.
Step 4: Offset Against Other Periods
The remaining credit can be used to discharge Corporation Tax liabilities of other accounting periods of the same company.
Step 5: Group Surrender
Any balance may be surrendered to other group companies. This is a specific RDEC mechanism and not standard group relief.
Step 6: Other HMRC Liabilities
The credit is then applied against other outstanding liabilities, such as PAYE or VAT.
Step 7: Payable Credit
Only after all prior steps are completed does the final payable tax credit (cash payment) arise. Any remaining restricted amounts are carried forward.
When Does RDEC Become Payable?
A payable credit typically arises where:
The company has a low or no Corporation Tax liability, and
The credit is not fully absorbed in earlier steps
However, even loss-making companies may not receive the full amount in cash due to the PAYE/NIC cap.
This is a critical point:
Being loss-making does not guarantee a full cash credit.
The PAYE/NIC Cap: A Common Risk Area
The PAYE/NIC cap remains one of the most frequent sources of error.
Practitioners must ensure:
Payroll records of the claimant company used in calculating the cap are correct
Inclusion of any connect company supplied externally provided workers (EPWs) is correct
Group payroll structures are properly reflected
Incorrect calculations here are a common trigger for HMRC scrutiny.
Group Considerations
In group scenarios, Steps 4 and 5 introduce additional complexity.
Key considerations include:
Which entity utilises the credit first
Whether surrendering or retaining a credit is more beneficial
Interaction with differing Corporation Tax profiles across the group
Sequencing decisions can materially impact cash flow.
Why the Full 7-Step Breakdown Must Be Disclosed
Including a detailed step-by-step computation is not just best practice—it is essential. Without it your claim will not be accepted by HMRC.
HMRC Transparency
A clear audit trail demonstrates that the statutory process has been followed.
Tracking Carry Forwards
Restrictions arising at Step 2 (notional tax) and Step 3 (PAYE/NIC cap) must be tracked accurately across accounting periods.
Group Clarity
Detailed disclosure ensures correct treatment across entities and accounting periods.
The Hidden Risk: Outdated Tax Software
Despite the maturity of the rules, some tax software still fails to correctly handle:
Notional tax calculations
PAYE/NIC caps
Proper step sequencing
Group surrender logic
If your software produces only a final figure without a detailed breakdown, or is shows just some of the steps, it is not sufficient.
Practitioners must:
Review outputs critically
Perform manual checks where necessary
Override or supplement computations where required
Final Thought
The RDEC regime is not inherently complex—but it is rigid.
Mastering the seven steps, understanding the constraints and ensuring full transparency in your computations is essential to delivering compliant and accurate claims.
Do not let software dictate your compliance position.
Control the calculation.
Visit HMRC's RDEC Steps help page.
Page updated
Google Sites
Report abuse