Calculate the Patent Box benefit: an effective 10% corporation tax rate on patent profits, scaled by the R&D nexus fraction.
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Computes the Patent Box deduction that brings the corporation tax rate on relevant IP profits down to an effective 10% — scaled by the nexus (R&D) fraction: (in-house + unconnected subcontracted R&D) × 1.3, capped at 1, over total qualifying expenditure including connected-party R&D and IP acquisition costs.
£500,000 of relevant IP profits at the 25% CT rate with fully self-developed IP: £300,000 deduction, £75,000 of tax saved — an effective 10% rate on the IP profits.
Enter the relevant IP profits (net of routine and marketing returns).
Set your marginal corporation tax rate.
Fill the nexus inputs: in-house R&D, subcontracted R&D and IP acquisition costs.
Read the deduction, the tax saved and the effective rate on IP profits.
Last data update
July 5, 2026
Sources and references
GOV.UK — Corporation Tax: the Patent Box (gov.uk/guidance/corporation-tax-the-patent-box).
The data in this calculator is updated regularly to reflect the latest official rates. When in doubt, consult the official sources listed above.
An effective 10% corporation tax rate on profits attributable to qualifying patents — delivered as an extra trading deduction rather than a separate rate.
Patents granted by the UK IPO or the European Patent Office (plus some EEA national offices), where the company holds or exclusively licenses the patent and has developed it.
A ratio ensuring relief follows real R&D activity: your own and unconnected subcontracted R&D (with a 30% uplift) divided by total qualifying expenditure including acquired IP — capped at 1.