Unity of invention meaning

In patent practice, unity of invention means a patent application may claim only one invention, or a group of inventions linked by a single general inventive concept. The link is a common “special technical feature” that makes a contribution over the prior art. The requirement is set in legislation: section 14(5)(d) of the Patents Act 1977 (UK), Article 82 and Rule 44 EPC, and PCT Rule 13. Irish patent law and EPC practice apply the same test, so usage is consistent across England & Wales, Scotland, Northern Ireland and Ireland. Examiners at the UKIPO, EPO and under the PCT may raise a lack of unity objection (including a posteriori, after the search). Practical outcomes include: restricting the claims to one inventive concept; paying additional search fees (EPO/PCT) for further inventions; or pursuing other inventions via divisional applications. If not remedied, lack of unity can lead to refusal or leave subject-matter unsearched and unexamined. Unity of invention is therefore a core patent prosecution requirement, shaping claim drafting, search strategy and filing tactics, and ensuring that granted patents protect a single inventive contribution.