Pillar Guide · Updated June 2026

UK Patent Box: Complete Guide to 10% Corporation Tax on IP Profits 2026/27

The UK Patent Box allows companies to elect a 10% corporation tax rateon profits derived from qualifying patents granted by the UK IPO, the European Patent Office, or specified EEA patent offices. Against the standard 25% CT rate this represents a 15 percentage point saving on every pound of qualifying IP profit. The regime uses the OECD nexus approach to ensure the benefit is linked to genuine in-house R&D activity. This guide explains qualifying patents, the streaming method for calculating qualifying profits, the nexus fraction, the formal election process, interaction with R&D tax credits, and a worked example.

Last updated: 10 June 2026Last reviewed: 10 June 2026How we verify

Key Patent Box figures -- 2026/27

Patent Box CT rate: 10% on qualifying IP profits
Standard CT rate (profits over £250k): 25%
Saving vs main rate: 15 percentage points per £ of qualifying IP profit
Qualifying patents: UK IPO, EPO and specified EEA patent offices
Election window: within 2 years of accounting period end
Nexus approach: OECD BEPS-compliant, applied since July 2016
Pending patent relief: retrospective claim up to 6 years after grant

What is the Patent Box

The UK Patent Box is a preferential corporation tax regime designed to incentivise companies to develop and commercialise patented technology in the UK. It was introduced by Finance Act 2012, first available from April 2013 and fully phased in by April 2017. The regime is elective -- companies choose whether to enter it for each accounting period.

The policy intent is to make the UK an attractive location for both developing intellectual property and exploiting it commercially, competing with similar regimes in the Netherlands (Innovation Box), Luxembourg (IP Box), Switzerland, and Ireland. HMRC estimates the Patent Box reduces UK tax revenues by approximately £1.1 billion per year but that the resulting R&D investment and IP retention generates broader economic benefits.

Companies that elect into the Patent Box separate their trading profits into "qualifying IP profits" (taxed at 10%) and "other profits" (taxed at the standard CT rate of 19% for small profits or 25% for larger companies). The calculation of qualifying IP profits involves identifying Relevant IP Income, deducting routine and marketing returns, and applying the nexus fraction.

The regime applies to UK companies subject to UK corporation tax. Overseas branches and non-UK resident companies are generally outside scope. Groups with overseas IP holding structures face additional complexity under the nexus fraction rules.

Qualifying Patents (UK IPO and EPO)

To use the Patent Box, the company must be the registered holder (or exclusive licensee) of at least one qualifying patent. Qualifying IP rights include:

UK patents granted by the Intellectual Property Office (UK IPO).
European patents granted by the European Patent Office (EPO) designating the UK.
Patents from specified EEA countries: Belgium, Bulgaria, Czech Republic, Denmark, Estonia, Finland, France, Germany, Hungary, Poland, Portugal, Romania, Slovakia and Sweden.
Supplementary Protection Certificates (SPCs) extending the term of a qualifying patent.
Plant variety rights under the Plant Varieties Act 1997.
Marketing authorisation data exclusivity rights for specified medicines under UK regulatory law.

US patents, Chinese patents, Japanese patents and patents from most other non-EEA countries do not qualify. A company with a global patent portfolio must identify specifically which patents are qualifying -- the Patent Box benefit applies only to profits attributable to the qualifying IP, not to the overall product or technology.

A company must also satisfy a "development condition" -- it must have performed a "qualifying development" on the patented invention. This means the company must have created or significantly developed the invention, or performed a significant amount of active management and exploitation. Simply acquiring a patent and licencing it without any development involvement fails this test.

Calculating Qualifying Profits (Streaming Method)

The streaming method (the default method for Patent Box since the July 2016 reform) calculates qualifying IP profits on a patent-by-patent or sub-stream basis. The five steps are:

Identify Relevant IP Income (RIPI) -- the income attributable to the qualifying patent (see below).
Deduct routine return -- 10% of "qualifying expenditure" (broadly, eligible operating costs excluding R&D and acquisition costs) represents the assumed arm's-length return on routine business functions. This is subtracted from RIPI.
Deduct marketing asset return -- an estimate of profits attributable to marketing intangibles (brand, customer relationships) rather than the patent. Companies may agree a "notional marketing royalty" with HMRC or use the default method.
Apply the nexus fraction -- multiply the remaining profit by the nexus fraction to reflect the proportion of R&D conducted in-house (see nexus section).
The result is the qualifying residual profit -- taxed at 10% Patent Box rate.

A simplified small claims method is available for companies with total qualifying IP profits below £1 million -- this uses a flat 75% of IP profits as qualifying rather than the full streaming calculation. The simplified method is substantially less accurate but reduces compliance cost for smaller Patent Box claims.

Relevant IP Income Definition

Relevant IP Income (RIPI) is the income that qualifies to flow into the Patent Box calculation. It encompasses:

Product income: sales income from products that incorporate a qualifying patent, restricted to the proportion attributable to the patented features via a notional royalty calculation.
Licence income: royalties and licence fees received from third parties for the right to use the qualifying patent.
Damage and compensation income: amounts received as damages for patent infringement, compensation for compulsory licensing, or insurance receipts related to patent rights.
Patent disposal income: proceeds from the outright sale of a qualifying patent.
Notional royalty: where no separate royalty is charged (e.g. a vertically integrated manufacturer), the company calculates a notional royalty that an arm's-length licensee would pay. This represents the RIPI from manufacturing and selling patented products in-house.

Income from products where the patent merely provides a marginal feature (not substantive to the product's commercial value) may be challenged by HMRC. The "notional royalty" approach requires careful benchmarking -- HMRC will scrutinise inflated notional royalties particularly in group transactions.

The Nexus Approach (OECD BEPS)

The nexus approach was mandated by the OECD's BEPS Action 5 report and required all participating countries (including the UK) to reform their IP tax regimes to link the benefit to genuine R&D activity in the taxing country. The UK implemented the nexus approach from 1 July 2016 for new entrants (and from 2021 for all companies under grandfathering transitional rules).

The nexus fraction is:

Nexus fraction = (D + S1) / (D + S1 + S2 + A)

D = direct R&D expenditure by the company
S1 = R&D subcontracted to unconnected third parties
S2 = R&D subcontracted to connected parties (group companies)
A = acquisition cost of qualifying IP

A company that does all its R&D in-house (D only, no S2 or A) has a nexus fraction of 1.0 -- no reduction to qualifying profits. A company that acquires IP or outsources R&D to group companies will have a fraction below 1.0, reducing its Patent Box benefit proportionally.

There is a 30% uplift provision: where D + S1 is below D + S1 + S2 + A, the numerator can be uplifted by 30% (subject to a cap of the total denominator). This softens the nexus reduction where a small amount of outsourced or acquired activity is present alongside substantial in-house R&D. Good record-keeping of R&D expenditure by category (in-house vs connected outsourced) is essential for nexus fraction calculations.

Making the Election

The Patent Box election is made by the company on its Corporation Tax return (CT600 supplementary pages). Key procedural points:

Election deadline: within 2 years of the end of the accounting period to which the election relates. A late election cannot be accepted.
Period of effect: once elected, the Patent Box regime continues for all subsequent periods until the company formally deselects.
Deselection: the company can opt out by notifying HMRC within 2 years of the relevant period end. After deselection there is a minimum 5-year exclusion period before re-election can take place.
No separate registration: the election is made on the CT return -- there is no prior registration or advance clearance process (though HMRC's Non-Statutory Business Clearance service can be used for complex structural questions).
Group elections: each group company must elect separately -- a group election does not exist. However, qualifying IP income can flow from IP-holding group companies to other group members through intra-group licences at arm's-length royalty rates.

The detailed Patent Box calculations are typically set out in a supplementary computation submitted with the CT600. HMRC may open enquiries into Patent Box computations, particularly where the nexus fraction or notional royalty calculation is complex. Advance preparation of detailed workings and supporting benchmarking analysis is strongly recommended.

Interaction with R&D Tax Credits

R&D tax credits and the Patent Box are complementary incentives and can apply to the same underlying technology. The key interaction points:

R&D credits reduce cost base: the R&D Expenditure Credit (RDEC, merged regime from April 2024) is taxable and above-the-line -- it reduces the effective R&D cost base. A lower cost base means potentially higher qualifying IP profit in the Patent Box calculation (beneficial).
SME enhanced deduction: under the legacy SME R&D scheme (for accounting periods before April 2024 under the merged regime), enhanced deductions for R&D reduced profits, potentially reducing the Patent Box calculation base. Companies should model the combined optimum claim.
No double-counting bar: the same R&D expenditure can generate both R&D credits and form part of the nexus fraction numerator (D and S1). There is no statutory bar on claiming both.
Timing: R&D credits arise in the period expenditure is incurred. Patent Box benefit arises in the period qualifying IP profits are generated (typically after the patent is granted and the technology is commercially exploited). The two reliefs often apply to different accounting periods.

Tax advisers should model R&D and Patent Box jointly from the outset of a technology project, as decisions about IP ownership structure, R&D outsourcing and patent jurisdiction have long-term consequences for both reliefs.

Worked Example

Profile: a UK SME manufacturer with a single qualifying UK IPO patent on a component used in its product range. All R&D was conducted in-house (nexus fraction = 1.0). Annual figures:

Total company profits: £500,000
Relevant IP Income (notional royalty on patented product): £200,000
Less: routine return (10% of £300,000 qualifying costs): £30,000
Less: marketing asset return (estimated nil -- no significant brand premium): £0
Qualifying residual profit before nexus: £170,000
Nexus fraction: 1.0 (all in-house R&D)
Qualifying IP profit (Patent Box): £170,000
Other profit: £330,000

Corporation tax calculation:

Patent Box profit: £170,000 x 10% = £17,000 CT
Other profit: £330,000 -- effective rate approx. 24% (marginal rate applies at £500k) = approx. £79,200 CT
Total CT: approx. £96,200
CT without Patent Box on full £500,000 at marginal 24%: approx. £120,000
Annual Patent Box saving: approx. £23,800

For a company spending £10,000 per year in professional fees to maintain the Patent Box claim, the net annual benefit is approximately £13,800. As qualifying profits grow, the case for Patent Box becomes stronger. A company generating £500,000 of qualifying IP profit at the 25% main rate saves £75,000 per year from the Patent Box.

Frequently Asked Questions

What is the UK Patent Box and what rate does it offer?

The UK Patent Box is an optional corporation tax regime that allows companies to apply a reduced 10% CT rate to profits derived from qualifying patents and certain other intellectual property rights. It was introduced in April 2013 and phased in fully by April 2017. Companies that elect into the Patent Box can separate their qualifying IP profits from their other profits and pay CT at 10% on the qualifying portion rather than at the standard 25% rate (for profits above £250,000) or small profits rate of 19% (for profits below £50,000). The saving on qualifying profits against the 25% main rate is 15 percentage points per pound of IP profit.

Which patents qualify for the Patent Box?

Qualifying patents are patents granted by: (1) the UK Intellectual Property Office (UK IPO); (2) the European Patent Office (EPO) covering the UK; (3) the patent offices of specified EEA countries (Belgium, Bulgaria, Czech Republic, Denmark, Estonia, Finland, France, Germany, Hungary, Poland, Portugal, Romania, Slovakia and Sweden). Patents granted by other countries do not qualify. In addition to patents, certain other IP rights qualify: Supplementary Protection Certificates (SPCs) extending the life of a patent, plant variety rights, and data exclusivity rights for certain medicines under UK regulatory law. Software patents are eligible if they meet the standard patentability tests.

How does the streaming method calculate qualifying IP profits?

The streaming method (also called the "new regime" method since the 2016 OECD reform) calculates qualifying IP profits on a patent-by-patent or product-by-product basis. For each qualifying patent stream: (1) identify the Relevant IP Income (RIPI) -- the revenue attributable to that patent; (2) deduct the routine return (10% of eligible costs, representing a deemed return on non-IP activities); (3) deduct the marketing asset return (the profit attributable to marketing intangibles such as brand); (4) apply the nexus fraction (D+S1) / (D+S1+S2+A) to adjust for in-house vs outsourced R&D; (5) the result is the qualifying IP profit taxed at 10%. Companies can alternatively use a simplified method for smaller Patent Box claims (below £1 million qualifying profit).

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What counts as Relevant IP Income (RIPI)?

Relevant IP Income is the income attributable to the exploitation of qualifying patents. It includes: (1) sales income from patented products -- the proportion of the product's income attributable to the patent, using a "notional royalty" calculation if the patent covers only part of the product; (2) royalties and licence fees received from licensing the patent to third parties; (3) damages, compensation and insurance receipts in respect of infringement of the qualifying patent; (4) proceeds from the sale of the patent itself. Income from manufacturing a patented product is RIPI only to the extent the income is attributable to the patented features -- a "small claims" apportionment is available for companies whose qualifying profits are below £1 million.

What is the nexus approach and how does it affect Patent Box claims?

The nexus approach was introduced from July 2016 following OECD Base Erosion and Profit Shifting (BEPS) Action 5, which requires preferential IP regimes to link the tax benefit to substantive R&D expenditure in the taxing jurisdiction. The nexus fraction is calculated as (D+S1) / (D+S1+S2+A) where D = direct qualifying R&D expenditure, S1 = R&D subcontracted to unconnected parties, S2 = R&D subcontracted to connected parties (group companies), and A = acquisition cost of the IP. The fraction reduces the qualifying IP profit if significant R&D was outsourced to connected parties or the IP was acquired rather than developed in-house. Companies that conducted all their own R&D domestically get a nexus fraction of 1.0 (no reduction).

How does a company elect into the Patent Box?

A company elects into the Patent Box by making a formal election to HMRC for a specific accounting period. The election must be made within 2 years of the end of the accounting period to which it relates. Once elected, the Patent Box regime continues for all subsequent periods unless the company opts out (by notifying HMRC of a deselection -- again within 2 years of the relevant period end). A company can opt out and back in, but this capability has anti-avoidance restrictions. The election is made on form CT600 supplementary pages or via HMRC's Corporation Tax online service. There is no separate registration process -- the election is made as part of the CT return.

Can a company use both Patent Box and R&D tax credits on the same IP?

Yes, subject to specific interaction rules. R&D tax credits (whether the SME scheme or the merged R&D Expenditure Credit from April 2024) reduce the cost base on which the Patent Box calculation is built -- higher R&D credits mean lower net costs and therefore potentially higher qualifying IP profits (which is beneficial). However, the two reliefs operate at different stages: R&D tax credits reduce the corporation tax liability or provide a cash credit in the period the R&D is incurred; Patent Box reduces the CT rate on resulting IP profits in subsequent periods when the patent is exploited commercially. There is no double-counting and both can legitimately apply to the same underlying R&D activity.

Is the Patent Box worth it for small companies?

For small companies with profits below £50,000 (standard rate 19%), the Patent Box reduces CT from 19% to 10% on qualifying IP profits -- a 9 percentage point saving. For companies in the marginal rate band (profits between £50,000 and £250,000, effective rate up to 26.5%), the saving against the effective marginal rate can be even larger. The administrative cost of maintaining a Patent Box claim -- tracking qualifying R&D, calculating nexus fractions, applying streaming -- typically costs £5,000 to £20,000 per year in professional fees. For small companies with very modest IP profits, the saving may not exceed the compliance cost. A rough rule of thumb: Patent Box is worthwhile if qualifying IP profits exceed £30,000 to £50,000 per year.

Can a company claim Patent Box on a product that contains multiple patents?

Yes. Where a product incorporates multiple qualifying patents, each patent is assessed separately under the streaming method or the company may use sub-stream groupings. A simpler alternative for products with multiple qualifying patents is the "notional royalty" method -- the company calculates a notional royalty that arm's-length parties would pay for the right to use the patented technology within the product. This notional royalty is the RIPI for that product. HMRC accepts various methods for calculating the notional royalty including comparable uncontrolled transactions, CUP data, and transfer pricing benchmarking. Expert economic analysis is often required for complex multi-patent products.

What happens if a patent application is still pending -- can we claim Patent Box?

Not directly -- Patent Box requires a granted patent. However, companies with pending patent applications can elect into the Patent Box regime in anticipation and then "bank" the qualifying profits from the period during which the application was pending. Once the patent is granted, the company can make a retrospective claim for Patent Box relief going back to the date the application was first published, up to a maximum of 6 years before the grant. This is the "pending patent relief" provision and can be very valuable for companies whose patents take several years to be granted but who are already generating commercial revenue from the underlying technology.

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About the author

Emma Clarke

UK Tax Writer

Emma Clarke has been writing about UK personal tax since 2018, with a particular focus on Self Assessment, PAYE coding and the practical mechanics of how HMRC actually applies the rules to ordinary salaries. Her work concentrates on translating the dense language of HMRC manuals and Finance Act schedules into worked examples that show, pound by pound, how income tax and National Insurance reduce a gross salary to the figure that lands in a UK bank account. Emma covers the full PAYE lifecycle: tax codes (1257L, BR, K codes, emergency codes), the Marriage Allowance, the High Income Child Benefit Charge, salary sacrifice arrangements and their effect on pensionable pay, the Apprenticeship Levy, and the differences between the rUK and Scottish income-tax regimes. She is particularly interested in the edge cases that catch PAYE employees out — the £100,000 personal-allowance taper, the 60% effective marginal rate it creates, and the interaction between student-loan plans and pension contributions. Every figure in Emma's articles is verified against the current HMRC rates pages and worked through a Self Assessment calculation by hand before publication. She writes to CalcHub's editorial standards: primary-source citations, plain English, no promotional language, and clear "this is general information, not financial advice" disclaimers where appropriate.

Personal-finance writer since 2018
UK tax specialism — PAYE, Self Assessment, National Insurance
Writes to CalcHub editorial standards (primary-source citation, annual review)

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Last updated: 10 June 2026How we verify

Disclaimer: This guide reflects UK Patent Box rules for 2026/27as of June 2026. Patent Box calculations -- particularly the streaming method, nexus fraction and notional royalty -- are technically complex and company-specific. HMRC may enquire into Patent Box computations. All Patent Box claims should be prepared with specialist IP tax advice. See gov.uk Patent Box guidance for HMRC's current published position.