R&D Tax Relief Calculator Guide: Worked UK Examples
How to calculate the potential tax benefit of qualifying R&D expenditure
Last reviewed 15 October 2026An R&D tax relief calculation begins with qualifying expenditure, but the value of the final tax benefit depends on the relevant scheme and the company's tax position.
For accounting periods beginning on or after 1 April 2024, the two principal schemes are:
- The merged R&D Expenditure Credit scheme (RDEC).
- Enhanced R&D Intensive Support (ERIS) for eligible loss-making R&D-intensive SMEs.
This guide demonstrates the financial calculations rather than repeating the rules for identifying qualifying expenditure.
For expense eligibility and allocation methods, see Qualifying R&D Expenditure.
These examples are educational calculations, not an automated calculator or personalised tax estimate.
1. Merged RDEC: Calculate the gross expenditure credit
For ordinary non-ring-fence trades, the merged RDEC provides a taxable expenditure credit equal to 20% of qualifying R&D expenditure.
Formula:
Gross RDEC = Qualifying expenditure × 20%
Example: £80,000 of qualifying expenditure
| Calculation | Amount |
|---|---|
| Qualifying R&D expenditure | £80,000 |
| Expenditure credit rate | 20% |
| Gross RDEC | £16,000 |
The gross credit is £16,000.
However, the expenditure credit is treated as taxable income. The eventual payment or tax benefit also depends on the statutory credit mechanism and the company's circumstances.
2. Gross credit versus net benefit
A common mistake is treating the gross RDEC amount as the final amount the business will retain.
Consider a simplified illustration using a 25% Corporation Tax rate on the taxable credit.
| Calculation | Amount |
|---|---|
| Gross RDEC | £16,000 |
| Illustrative Corporation Tax on the credit at 25% | £4,000 |
| Illustrative post-tax value | £12,000 |
The £12,000 figure illustrates the arithmetic effect of taxing the credit at 25%.
It is not a universal payment calculation.
The actual statutory mechanism can involve Corporation Tax liabilities, other tax debts, PAYE-related restrictions and offsets before payment.
Some companies may also be subject to different applicable Corporation Tax rates or special circumstances.
The company should calculate the final amount using the relevant rules, not simply multiply the gross credit by a standard net percentage.
3. ERIS: Calculate the enhanced expenditure
Eligible loss-making R&D-intensive SMEs may qualify for ERIS.
ERIS uses an additional deduction of 86% of qualifying expenditure.
This produces an enhanced expenditure amount of 186% of the original qualifying expenditure.
Formula:
Enhanced expenditure = Qualifying R&D expenditure × 186%
Example: £80,000 of qualifying expenditure
| Calculation | Amount |
|---|---|
| Qualifying R&D expenditure | £80,000 |
| Additional 86% deduction | £68,800 |
| Enhanced expenditure | £148,800 |
The company's available surrenderable loss must then be established.
The payable credit is calculated at 14.5% of the lower of the enhanced expenditure and the relevant surrenderable trading loss, subject to applicable restrictions.
4. Why surrenderable losses matter
Suppose a company has £80,000 of qualifying R&D expenditure, creating enhanced expenditure of £148,800.
However, its surrenderable trading loss after the applicable calculation is only £110,000.
The calculation is:
| Calculation | Amount |
|---|---|
| Enhanced expenditure | £148,800 |
| Surrenderable trading loss | £110,000 |
| Lower amount | £110,000 |
| Payable credit rate | 14.5% |
| Illustrative payable credit | £15,950 |
Even though enhanced expenditure is £148,800, the credit is calculated on £110,000.
This example assumes the company meets ERIS eligibility conditions and that no other restriction reduces the payment.
What if the company has sufficient losses?
If its surrenderable loss were at least £148,800, the corresponding illustrative credit would be:
£148,800 × 14.5% = £21,576
That is equivalent to 26.97% of the original £80,000 expenditure, but only under the stated conditions.
It should not be presented as a guaranteed rate for every loss-making SME.
5. Compare financial scenarios
The following table illustrates the calculations for different amounts of fully qualifying expenditure.
| Qualifying expenditure | Gross merged RDEC at 20% | ERIS maximum illustration at 26.97% |
|---|---|---|
| £25,000 | £5,000 | £6,742.50 |
| £50,000 | £10,000 | £13,485 |
| £100,000 | £20,000 | £26,970 |
| £200,000 | £40,000 | £53,940 |
The RDEC column shows gross taxable credits.
The ERIS column assumes the company is eligible and has sufficient surrenderable losses, with no other applicable payment restrictions.
The two columns are not equivalent net-cash outcomes.
6. What is the R&D intensity threshold?
To qualify for ERIS, an SME generally must be loss-making and meet the applicable R&D intensity condition.
For accounting periods beginning on or after 1 April 2024, the standard threshold is 30%.
The intensity calculation compares qualifying R&D expenditure with the relevant total expenditure, including connected-company expenditure where the rules require it.
This is not necessarily the same as dividing R&D costs by turnover or the company's accounting expenses.
Special rules, including a grace period, may apply.
A company should confirm eligibility using the current HMRC guidance before calculating an ERIS credit.
7. What can change the final result?
The simplified examples above do not account for every statutory requirement.
Actual benefits may differ because of:
- The company's applicable accounting period and scheme.
- The amount of verified qualifying expenditure.
- Corporation Tax treatment.
- Trading losses available for surrender.
- R&D intensity and connected-company rules.
- PAYE and National Insurance-based credit caps.
- Other tax liabilities or offsets.
- Northern Ireland-specific requirements.
- Historic relief rules for earlier accounting periods.
For example, the general PAYE cap for the new schemes is £20,000 plus 300% of the company's relevant PAYE and National Insurance liabilities, subject to the statutory exemptions and mechanisms.
The calculation should therefore distinguish the theoretical relief amount from the amount that may ultimately be paid or used.
8. How Plio supports R&D cost preparation
Plio helps businesses prepare the technical and financial information supporting their R&D tax relief claims.
It supports the organisation of R&D project records, relevant costs and supporting allocation information.
Lister AI focuses on evaluating technical evidence, including explanations of scientific or technological uncertainties and advances.
Plio does not provide a guaranteed tax benefit calculation or submit a Corporation Tax claim to HMRC.
Businesses should verify their relief calculation against their actual tax position and the relevant HMRC rules.
Organise your R&D evidence and costs before preparing your tax calculation.
Official HMRC references
All examples are simplified and assume the stated eligibility conditions. They are not tax advice.
Published by: Plio — Paylists LTD
Prepared and reviewed by: Muly Zohar, Founder & Product Architect
Last published:
Sources: Official HMRC guidance and other references linked in this article.
General information only. Plio is not a tax advisory service. Read about our content responsibility and review