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"In China, there is no doctrine preventing an applicant from obtaining multiple patents for obvious variants, patentably indistinct subject matter, or incremental improvements, so long as the claims are not identical in scope." - Michael Huang
Double patenting doctrine worldwide builds on the principle that an inventor is entitled to only one patent for each invention. Obtaining multiple patents on the same invention could circumvent this principle by extending exclusivity beyond statutory expiry.
On its face, the principle is simple enough. In practice, "same invention" is not a simple concept at all: variations in local rules and interpretations-including different approaches to issues such as claim scope and construction; obviousness (in the "patentably distinct" context); amendments limits; and shifting claim sets when multi-application families exist-converge to create a panoply of double patenting regimes internationally. The resultant complexity can be a minefield for applicants filing patents in various jurisdictions.
Divisionals are the most common source of double patenting issues in all major patent systems. They're important because they inherit the parent's filing date, priority claims, and disclosure. They're also an important aspect of strategic claim management and filed for diverse reasons: to pursue broader or narrower claims, different claim categories, fallback positions, or commercial, real-world embodiments not embraced by the priority claims.
In three articles, this series will review the double patenting regime in China, Hong Kong, and Southeast Asia; New Zealand and Australia; and Canada.
China
Article 9(1) of the Peoples Republic of China's Patent Law prohibits only where two patents claim the same invention or creation, known as the "strict identity" test.
"Double patenting issues arise no matter when the applications are filed or whether the applications are still pending or already granted," says Michael Huang, special counsel in the Hong Kong office of Spruson & Ferguson, a member of the IPH network. "The issue most commonly arises in same day dual filings involving invention and utility models, but it also is common in filings embracing two invention patents or two utility models."
According to Huang, double patenting exists in China only if at least one claim in a patent has the same scope as a claim in another patent.
"If claim scopes differ, there is no double patenting. Differences in technical features, claim breadth, or combinations defeat a same-invention finding."
The upshot is that the country does not recognise obviousness-type double patenting (OTDP).
"There is no doctrine preventing an applicant from obtaining multiple patents for obvious variants, patentably indistinct subject matter, or incremental improvements, so long as the claims are not identical in scope," Huang explains.
Before 1 January 2026, China granted millions of invention + utility model (UMs) patents. Historically, examiners did not substantively examine UMs, which they granted within six to 12 months (the invention patents typically took years) and were enforceable immediately. These powerful attributes made them highly effective enforcement tools.
As of 1 January 2026, however, China has significantly restricted same-day invention + utility model filings. The key features of the change, Huang explains, are:
- Applicants must declare the dual filing in both applications;
- For declared cases, if the invention is allowable, the applicant must abandon the utility model to obtain the invention grant;
- China no longer allows applicants to amend claims to differentiate scope with the intention of having both applications allowed; and,
- Undeclared filings trigger standard Article 9 rejection (only one grant possible) but may preserve amendment flexibility.
Although the Patent Law lists double patenting as a ground for invalidation, double patenting objections in litigation are less common than novelty and inventiveness challenges.
"Because the CNIPA [China National Intellectual Property Administration] generally examines same-invention situations carefully during substantive examination, especially for invention + utility model dual filings, many potential double patenting conflicts are filtered out before the grant," Huang states.
But, Huang cautions, applicants or litigants should not take the relative infrequency of double patenting challenges as a sign that they may disregard the issue.
"Practitioners should continue to monitor claim scope carefully across related Chinese filings."
Hong Kong
Like China, Hong Kong expressly prohibits same-invention double patenting, but only for those patents that undergo substantive examination, and not for those filed by way of the re-registration process.
"Hong Kong patent law is statutory in this respect," Huang states. "The Patents Ordinance limits double patenting only to situations involving the same invention, not obvious variants or patentably indistinct subject matter."
Under Hong Kong law, double patenting occurs where two patents or applications relate to the same invention; have the same inventor or share a common inventor; and, have the same material date (filing date or priority date).
"This prohibition applies both during substantive examination of standard patents and post-grant substantive examination of short-term patents," Huang states. "It is effectively a strict identity or 'same scope in substance' test."
And also like China, Hong Kong does not have a non-statutory or judicially created OTDP doctrine.
The upshot is that examiners deal with inventive step or obviousness issues only under the statutory requirement in section 9C of the Ordinance.
"Hong Kong law rejects policy-driven OTDP concepts and instead relies on novelty, inventive step, and priority rules to police claim scope," Huang explains. "It does not repurpose these issues as a time-extension of anti-harassment doctrine between commonly owned patents."
The upshot is that obvious variants, improvement, or overlapping elements do not trigger double patenting issues if their scope is substantively different.
Southeast Asia (SEA)
On casual review, there is a certain homogeneity among the SEA countries that have meaningful double patenting regimes: Singapore, Malaysia, Philippines, Indonesia, Thailand, and Vietnam.
In particular, these countries limit double patenting to instances where the "same invention" (or some variation of that term, like "identity") is claimed in the various patents. As well, no SEA country recognises OTDP.
But examiners in the various jurisdictions do not necessarily approach "same invention" or "identity" in the same way.
Singapore, Malaysia, and Philippines stand out because they have explicit guidelines for determining how examiners determine "identity" of claims. Although the various guidelines may point in different directions, they at least introduce an element of certainty into double patenting determinations.
"Many of the Southeast Asia countries do not really have a clear definition for determining what amounts to double patenting", says Singapore-based Maik Brinkmann Spruson & Ferguson's life sciences practice group leader for Asia. "Examiners in these countries tend to apply their own understanding without the assistance of guidelines."
Singapore features the Singapore Examination Guidelines, which implements section 80 of the Patents Act. They are clear that double patenting arises when two applications (or an application and a granted patent) with the same applicant or successor in title claim the same priority date and contain claims that are identical in scope.
The Singapore Guidelines, then, do not allow identity but do allow overlap. Still, examiners check all "parallel applications"-meaning two or more applications that coexist, share the same priority date, and have the same applicant-for double patenting issues.
By contrast, Thailand has no guidelines, and examiners have broad discretion because their examination culture emphasises individual judgment over rigid rules. Accordingly, they tend to interpret "identity" in a substantive, non-literal way.
By contrast, some SEA countries without detailed guidelines, such as Indonesia, Vietnam, and others treat "identity" literally, so even trivial wording differences can avoid double patenting findings.
All of which is not to say that there are no double patenting issues in Singapore. Issues can arise as to whether different wording in claims amounts to a difference in scope; whether the added features in a claim don't actually narrow the claim; and, as mentioned specifically in the Guidelines, when applicants try to avoid double patenting by using a generic group in one application while the other application uses a more specific feature encompassed by the generic group.
Quite apart from the existence of guidelines, however, local quirks abound.
For example, Malaysia's system automatically flags "parallel" applications, which examiners routinely cross-check. The regime also leans to using the same examiners or linked examiners for an entire family.
"The result is that applicants get very early notice of double patenting issues, often in the first action and even before they receive notice of substantive novelty and inventive-step objections," Brinkmann says.
The same is true in the Philippines, where divisionals are common: regulators review the entire family at the outset of examination, treating double patenting as a threshold issue.
The upshot, then, is that practitioners and clients seeking to file in SEA should proceed with caution originating in an awareness that interpretations of "same invention" can vary widely by jurisdiction.
The content of this article is intended to provide a general guide to the subject matter. Specialist advice should be sought about your specific circumstances.
