How Does the Patent Box Work? A Complete Guide for UK SMEs

If your company holds a patent — or is developing something patentable — the Patent Box can cut the Corporation Tax on the profits that patent generates to an effective 10%, against a main rate of 25%. For a profitable, innovative SME that is a substantial, permanent saving, yet it remains one of the most under-claimed reliefs in the UK tax system.

This guide explains, in plain English, how the Patent Box actually works: who qualifies, what counts as relevant income, how the benefit is calculated, and how it fits alongside R&D tax relief. For the headline overview of what we do here, see our Patent Box service page; this article is the detailed how-it-works walkthrough.

What the Patent Box is

The Patent Box is a UK Corporation Tax relief, introduced in 2013 and fully phased in by 2017, that lets a company apply a 10% effective tax rate to the profits it earns from qualifying patented inventions. It rewards companies that both own the rights to an invention and have done the work to develop it.

The relief is deliberately generous because it is meant to keep high-value innovation — and the profits from it — in the UK. Since the Corporation Tax main rate rose to 25% in April 2023, the gap between the standard rate and the 10% Patent Box rate has widened, so the relief is worth considerably more today than it was when many companies last looked at it.

Who qualifies: the three core conditions

To claim, a company must meet three conditions.

1. It must hold qualifying IP rights. The most common is a granted patent from the UK Intellectual Property Office (IPO) or the European Patent Office (EPO). Patents granted by certain EEA national offices also qualify, as do some other rights — supplementary protection certificates, and regulatory data protection (marketing exclusivity) for medicinal and plant-protection products. A pending application does not qualify yet, but once the patent is granted you can claim relief on the profits made while the application was pending (up to six years).

2. It must own or exclusively license the rights. You either own the patent or hold an exclusive licence that gives you rights to develop, exploit and defend the invention across at least one whole national territory.

3. It must meet the development condition. The company (or a group company) must have made a significant contribution to creating or developing the patented invention, or a product incorporating it. The Patent Box is not available to a business that simply buys in a patent and collects royalties without having done the underlying development work.

For groups there is an additional active ownership condition, which broadly requires the company holding the IP to perform a significant amount of management of that IP portfolio.

What income can go in the box

Once you qualify, the profits eligible for the 10% rate — "relevant IP income" — are wider than many people expect. They include:

• Sales of patented products — and, importantly, sales of a larger product that incorporates at least one patented component. The whole product's income can qualify, not just the patented part.
• Licensing income and royalties from letting others use the patent.
• Proceeds from selling patent rights.
• Infringement and damages income received for breach of your patent rights.
• Notional royalty — where you use a patented process internally (rather than selling a product), you can bring in a notional royalty representing what you would have paid to license it.

Income that has nothing to do with the patented technology — routine service revenue, non-patented product lines — stays outside the box and is taxed at the normal rate.

How the benefit is calculated

The Patent Box does not literally re-tax profits at 10%. Instead it works by giving an additional deduction from trading profits, calculated so that the relevant IP profit ends up taxed at an effective 10%. The steps, in outline:

1. Identify relevant IP income and strip out a routine return (a standard mark-up on certain operating expenses) and a marketing-intangibles return, to isolate the profit genuinely attributable to the patent.
2. Apply the R&D fraction (the "nexus" rules). Since 2016, the qualifying profit is scaled by how much of the underlying R&D you did yourself. The fraction rewards in-house R&D and R&D subcontracted to unconnected third parties, and penalises acquired IP and R&D subcontracted to connected parties. Companies must stream income and expenditure per patent (or per product/product-family) and keep records to support the fraction.
3. Apply the deduction so the isolated, nexus-adjusted profit is effectively taxed at 10%.

A simple worked example

Suppose an engineering SME makes £500,000 of profit from a patented product line. After removing the routine and marketing returns, £300,000 is treated as qualifying IP profit, and the company's R&D fraction is 1 (all the R&D was done in-house). Taxing £300,000 at 10% rather than 25% saves £45,000 in Corporation Tax for the year — every year the patent generates that profit. The numbers in a real claim need proper streaming and apportionment, but that is the shape of the prize.

How to elect into the Patent Box

The relief is not automatic — you must elect in. The election must be made within two years after the end of the accounting period in which the relevant profits (and income) arose. Miss that window and the benefit for that period is lost. In practice the election is made in the Company Tax Return computations, supported by the streaming calculations.

Because the two-year clock runs from the accounting period, not from when the patent is granted, it is worth reviewing eligibility as soon as a patent application is filed — so the records are in place by the time it is granted.

Patent Box and R&D tax relief work together

This is the point most SMEs miss. R&D relief and the Patent Box relieve different ends of the same innovation:

• R&D tax relief supports the cost of the development work — the input. If you're claiming under the merged RDEC scheme or ERIS, that's your input relief.
• The Patent Box rewards the profit the resulting patent goes on to earn — the output.

A company that does qualifying R&D, patents the result, and then sells it can legitimately claim both. If you want the distinction laid out in full, see our comparison of R&D relief versus the Patent Box. The two are complementary, not alternatives.

Is it worth it for a smaller company?

The Patent Box carries a real compliance overhead — streaming, the R&D fraction, and record-keeping — so it is not free. But for a profitable company with even one commercially important patent, the maths usually works comfortably in its favour, especially at a 25% main rate. The break-even is lower than most directors assume.

The commonest reasons SMEs don't claim are simply that they don't realise a patented product (not just licensed IP) qualifies, or they assume the admin outweighs the benefit without running the numbers.

Frequently Asked Questions

What is the Patent Box tax rate?

The Patent Box applies an effective 10% Corporation Tax rate to qualifying profits from patented inventions, compared with the 25% main rate. The saving is delivered as an additional deduction from trading profits rather than a separate 10% charge.

Do I need a granted patent to claim?

Yes — relief applies from the date a qualifying patent is granted, not while the application is merely pending. However, once granted you can claim for profits earned during the application period (up to six years back), provided you had elected in.

Can I claim R&D tax relief and the Patent Box at the same time?

Yes. They cover different things: R&D relief supports the cost of development (the input), while the Patent Box rewards the profit the resulting patent earns (the output). Companies that develop and patent their own technology commonly claim both.

How long do I have to elect into the Patent Box?

You must elect within two years after the end of the accounting period in which the relevant IP profits arose. Missing the deadline forfeits the relief for that period.

Does a product that only partly uses a patent qualify?

Often, yes. If a larger product incorporates at least one patented item, income from the whole product can be relevant IP income — one of the most valuable and least understood features of the regime.

If you hold a patent, or are developing something you expect to patent, it's worth checking whether the Patent Box applies before the two-year election window closes. Get in touch and we'll tell you quickly whether it's worth pursuing for your company.