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European Patent Convention · Search and examination procedure

Rule 164 EPC: Unity of invention and further searches

Annotated by , Co-founder and CEO, PatentAssist.ai
Updated

Text of Rule 164 EPC

(1) If the European Patent Office considers that the application documents which are to serve as the basis for the supplementary European search do not comply with the requirement of unity of invention, it shall:

(a) draw up a partial supplementary search report on those parts of the application which relate to the invention, or the group of inventions within the meaning of Article 82, first mentioned in the claims;

(b) inform the applicant that, for the supplementary European search report to cover the other inventions, a further search fee must be paid, in respect of each invention involved, within a period of two months; and

(c) draw up the supplementary European search report for the parts of the application relating to inventions in respect of which search fees have been paid.

Rule 164(1) EPC, excerpt. Full official text on epo.org

In plain English

Rule 164 is the Euro-PCT counterpart of Rule 64. It gives you a chance to have inventions searched that were not searched in the international phase, so that you can choose which one to pursue in Europe.

Rule 164(1) applies when the EPO draws up a supplementary European search, because another office was the ISA. If the claims on file at the end of the Rule 161(2) period lack unity, the EPO searches the first invention and invites further search fees, €1,595 each from 1 April 2026, within two months.

Rule 164(2) applies when there is no supplementary search, because the EPO was the ISA or supplementary authority. At the end of the Rule 161 period, the examining division checks for any invention in the claims that the EPO did not search, including inventions brought in from the description. It invites search fees within two months, and sends the results with the first Article 94(3) communication or a Rule 71(3) communication. These fees are not reduced, and cannot be paid before the invitation (Guidelines C-III, 3.1).

Only one Rule 164(2) invitation is sent. After that, you must limit the application to one searched invention, and claims to any unsearched invention have to go into a divisional. Unsearched subject matter in the description must be deleted or marked as outside the claims before grant.

Fees paid under either paragraph are refunded if you request it and the examining division finds the invitation unjustified (Rule 164(5)). Neither two-month period can be rescued by further processing (Rule 135(2)).

Deadlines and fees

Step Time limit Basis
Pay further search fees 2 months from the invitation; €1,595 per invention; no further processing Rule 164(1)(b) or (2)(a); Rule 135(2); RFees item 2
Claims assessed for unity As they stand at the end of the 6-month Rule 161 period Rules 161 and 164; Guidelines A-XIV, 1

Key decisions

  • G 2/92 : Subject matter for which no search fee is paid cannot be pursued in the application and must be pursued, if at all, in a divisional.

Common objections

Invention imported from the description

Moving to a new invention on entry triggers Rule 164(2) even if the claims are unitary. Pay to have it searched if you want to pursue it.

Request to limit to one invention

Choose one searched invention in reply to the Rule 164(2)(b) communication and adapt the description. Other searched inventions can go into divisionals.

Drafting and prosecution tips

  • Settle the claim set before the Rule 161 period ends; that set decides which inventions are flagged.
  • Pay further fees only for inventions you may want in this application; the rest can be divided out with their own search.
  • Ask for a refund in examination if you paid on an invitation you believe was wrong.

Related provisions

In the Guidelines for Examination (2026)

PatentAssist guides

All annotated EPC provisions

EPC excerpts are quoted from the European Patent Convention, 17th edition, as amended and published by the European Patent Office. Practice notes follow the Guidelines for Examination in the EPO (April 2026) and the Boards of Appeal decisions cited. Fees are those in force from 1 April 2026. This is general information, not legal advice: check the official text and confirm deadlines with a European patent attorney.