Understanding Double Patenting in Singapore and How It Compares with the EPO and US

09 Jul 2025

When building a strong patent portfolio, applicants often file multiple applications around a core technology. However, this strategy can backfire if not carefully managed, particularly when it comes to double patenting.

Double patenting arises when a single invention is protected by more than one patent filed by the same applicant. This practice is generally prohibited under patent law to prevent the unjustified extension of a patent’s term and to avoid overprotection of the same invention. While the concept of double patenting is recognized across major jurisdictions, the specific rules and associated risks can vary significantly.

Singapore
Section 80(1)(g) of the of the Patents Act provides that if the patent is one of two or more patents for the same invention having the same priority date and filed by the same party or the party’s successor in title, the court or the Registrar may, on the application of any person, revoke one of the patents.

The Singapore Patent Examination Guidelines state that the Examiner is empowered to assess double patenting during examination. A positive finding of double patenting is treated as an objection, and if the objection is not resolved, the application will not proceed to grant.

The test for whether two applications relate to the “same invention” is also set out in the Guidelines. Double patenting will apply if two claims are identical in scope, which typically occurs when the claims are coterminous. It also applies where the claims use different terminology but are identical in substance. This will include situations where different terminology is used to define the same invention.

The Examination Guidelines also provide that Examiners should focus on independent claims when assessing applications for double patenting. However, in practice, a double patenting objection may still be raised between a dependent claim in one application (Application A) and an independent claim in another application (Application B). If Application A is granted first, this could ultimately prevent the grant of Application B. This situation is particularly relevant in the pharmaceutical industry.

Accordingly, careful planning of the patenting strategy, including determining the scope of claims in each application, and sequential prosecution of applications, should be undertaken at an early stage.

The European Patent Office (EPO)
Unlike the Singapore Patents Act, the European Patent Convention (EPC) does not contain an explicit statutory provision addressing double patenting. However, the EPO Enlarged Board of Appeal, in decision G 4/19, confirmed that a prohibition on double patenting is applicable under Article 125 of the EPC.

In line with this, the EPO Examination Guidelines provide that a European patent application can be refused if it claims the same subject-matter as a European patent already granted to the same applicant. The Guidelines identify three typical scenarios where double patenting may arise — all of which are broadly analogous to Singapore’s requirement of “having the same priority date”:

• Two applications filed on the same day;

• A parent and its divisional application; and

• An application and its priority application.

The EPO Examination Guidelines do not provide an explicit guidance on what constitutes the “same subject-matter.” However, the following language appears to suggest that the EPO applies a standard similar to Singapore’s “identical in scope” test:
“Where two or more European applications from the same applicant … relate to the same invention, the applicant must amend one or more of the applications so that the subject-matter of their claims is no longer the same, … . If the claims of those applications only partially overlap, no objection should be raised … .”

Additionally, the Guidelines include an example that is similar to Singapore’s practice:
“… when, for example, the subject-matter of claim 1 in an application is the same as that of a dependent claim in a granted patent held by the same applicant, an objection of double patenting will be raised … .” 

The United States
The issue of double patenting in the United States is a complex one, generally categorized into two types:

1. Statutory double patenting under 35 U.S.C. § 101; and

2. Non-statutory or obviousness-type double patenting (ODP).

Statutory double patenting under 35 U.S.C. § 101
According to the Manual of Patent Examining Procedure (MPEP), the key question in assessing statutory double patenting is: Is the same invention being claimed twice?

Here, "same invention" refers to identical subject matter. A reliable test is whether a claim in the application (Application B) could be literally infringed without literally infringing a corresponding claim in the patent (Patent A). 

Importantly, a statutory double patenting rejection cannot be overcome by filing a terminal disclaimer. The only remedy is to cancel or amend the claims such that the two sets of claims are no longer coextensive in scope.