Rule 43 EPC: 7 Essential Rules for Patent Claims

A US claim set that sails through the USPTO can draw an objection on its first encounter with a European examiner. The reason is almost always Rule 43 EPC, the implementing rule that sets the form and content of claims in a European patent application. It controls how you cast an independent claim, how many you can file per category, how dependencies work, and even whether figure numbers belong in the claim. Here is what each of its seven paragraphs actually requires — and where transatlantic drafting habits get caught.

Most Rule 43 objections trace back to claim scope that was never tested against the European prior art before filing. A freedom-to-operate and claim-scope search shows you how wide an independent claim can safely run in Europe, and our patent drawing service at $25 per figure supplies the numbered figures your Rule 43(7) reference signs must match.

What Rule 43 EPC Covers

Rule 43 EPC sits in the Implementing Regulations to the European Patent Convention and fleshes out Article 84, which demands that claims be clear, concise and supported by the description. Where Article 84 states the principle, the rule gives the mechanics. Its seven paragraphs — set out in full in the EPO’s official legal text — tell you how to structure a claim, when you may file more than one independent claim in the same category, how dependent claims must refer back, how many claims are reasonable, and how reference signs and cross-references are handled.

None of this is optional window-dressing. An examiner who finds a claim set non-compliant can raise an objection that stalls prosecution until you amend. Getting the form right at filing — especially when you are converting a US-style set — saves an office-action round and the fees that come with it.

Rule 43(1): The Two-Part Form

Rule 43(1) says an independent claim should, “wherever appropriate,” be written in two parts: a preamble reciting the features that together are already known from the closest prior art, followed by a characterising portion — introduced by “characterised in that” or “characterised by” — reciting the features the invention adds.

Two words carry the weight. “Wherever appropriate” means the two-part form is strongly preferred but not mandatory; where it would obscure rather than clarify the invention, a one-part claim is acceptable. US practitioners, used to single-part claims, often draft the whole claim as a preamble and get asked to split it. The fix is to identify the closest prior art and move the inventive features behind the “characterised” dividing line.

Rule 43(2): One Independent Claim Per Category

This is the paragraph that surprises US applicants most. Rule 43(2) allows only one independent claim in each category — product, process, apparatus or use — unless the subject matter falls into one of three exceptions:

• (a) a plurality of interrelated products, such as a transmitter and a matching receiver
• (b) different uses of a product or apparatus
• (c) alternative solutions to a particular problem, where it is inappropriate to cover them in a single claim

The applicant bears the burden of showing an exception applies. A US set routinely carries two or three independent apparatus claims of similar scope; at the EPO those will draw an objection and you will be asked to pick one and recast the rest as dependents. Plan the claim architecture before you file, not after the examiner forces the choice.

Rules 43(3) and 43(4): Dependent Claims

Rule 43(3) permits a claim stating the essential features of the invention to be followed by one or more claims directed to particular embodiments — the dependent claims. Rule 43(4) sets how they refer back: a dependent claim includes all the features of the claim it depends on and must contain, if possible at the start, a reference to that claim before stating the added features. Dependent claims that refer back to the same claim or the same set of claims should be grouped together in the most sensible way.

Here Europe is more generous than the United States. A dependent claim may refer to another dependent claim, and multiple-dependent claims — one claim referring to several others in the alternative — are allowed, including a multiple-dependent claim that itself depends on a multiple-dependent claim. The EPO does not penalise them the way the USPTO does with per-claim multiple-dependency fees, so a US set stripped of its multiple dependencies to save fees at home can usually be restored for Europe.

Rule 43(5): Number and Numbering of Claims

Rule 43(5) requires that the number of claims be reasonable given the nature of the invention, and that claims be numbered consecutively in Arabic numerals. “Reasonable” is not a hard ceiling, but it connects to cost. Under the separate claims-fee rule, a European application attracts an additional fee for the sixteenth claim and each one after it, and a steeper fee from the fifty-first claim onward.

The practical discipline is to prune. A US set that ballooned to forty claims to capture every nuance can often be consolidated into fifteen or fewer for Europe without losing protection, which keeps you under the first fee tier. Consecutive Arabic numbering sounds trivial, but gaps or re-lettered claims after amendment are a common formality slip.

Rules 43(6) and 43(7): Cross-References and Reference Signs

Rule 43(6) says that, except where absolutely necessary, claims must not define the invention by referring to the description or the drawings — no “as described in paragraph 20” or “as shown in Figure 3” standing in for the actual feature. The claim has to recite the technical feature itself. Omnibus claims of the “substantially as described” type are effectively ruled out.

Rule 43(7) handles the opposite habit. Where the application has drawings with reference signs, the technical features in the claims should preferably be followed by those signs in parentheses when it increases clarity — and, critically, those reference signs are not to be construed as limiting the claim. So a bracketed figure number does not narrow your scope. In a two-part claim, signs belong in both the preamble and the characterising portion, not just one.

Where Europe and the United States Diverge

Most Rule 43 objections trace back to a handful of assumptions that are correct in US practice and wrong at the EPO. Seeing them side by side makes the conversion faster:

• Independent claims: the USPTO lets you file several of similar scope in one category; the EPO expects one per category absent a 43(2) exception
• Claim form: US claims are typically single-part; Europe prefers the two-part ‘characterised in that’ structure wherever it reads clearly
• Multiple dependencies: the USPTO charges extra and bars a multiple-dependent claim from depending on another; the EPO allows both freely
• Reference signs: rarely used in US claims, expected in European claims — and expressly non-limiting under 43(7)
• Claim count: US sets often run large; European claims fees start biting at the sixteenth claim

None of these differences is a matter of better or worse drafting. They reflect two systems that weigh clarity, prior art and fees differently, and a claim set that ignores the European assumptions simply costs an extra office action to fix. The EPO Guidelines for Examination, Part F, Chapter IV, walk through each requirement with worked examples if you want the examiner’s own reasoning.

Putting Rule 43 EPC to Work on a US Claim Set

When we adapt a US specification for Europe, the Rule 43 EPC pass is a short, repeatable checklist that heads off the most common formality objections:

1. Collapse multiple independent claims in each category down to one, unless a 43(2) exception genuinely applies
2. Recast the main claim in two-part form against the closest prior art where it reads clearly
3. Restore multiple-dependent claims the US set dropped for fee reasons
4. Trim the total to stay under the sixteen-claim fee threshold where you can
5. Strip cross-references to the description or figures out of the claim language
6. Add bracketed reference signs from the drawings to aid clarity, knowing they are non-limiting

Run that pass before filing and the European application usually clears examination on claim form without an avoidable objection. The same claims that are compliant in the United States are simply built on different assumptions, and Rule 43 is where those assumptions diverge.

Drafting Claims for Europe?

PerspireIP adapts US and PCT claim sets to EPO practice and supports European prosecution end to end — including validation once the patent grants. See our country guides, such as validating a European patent in the Netherlands, or contact us for a claim-set review before you file at the EPO.

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