Patent families: continuations, divisionals and CIPs
How US continuations, divisionals and CIPs relate to a parent, how foreign priority builds international families, and why families matter for FTO.
By the One Transform team6 min read
A patent family is a group of applications and patents linked by a shared parent application or a shared priority claim, and so by a shared disclosure. In the US, a family grows through continuations, divisionals and continuations-in-part, which claim the benefit of an earlier application's filing date. Across countries, it grows through foreign priority claims made within 12 months of the first filing. Those links decide which date each claim can rely on, when the patents expire and where the invention is protected.
Two kinds of family link
US continuity is a parent-and-child chain inside one office. A later US application claims the benefit of an earlier US application, usually to pursue different claims on the same disclosure.
Priority links filings in different offices. An applicant files first in one country, then files in others within 12 months and claims the first filing's date. Most real families combine both: a foreign first filing, a US application claiming its priority, and a US continuation chain hanging off that application.
US continuity: the application types
| Type | What it contains | Date its claims can rely on | Typical reason to file |
|---|---|---|---|
| Continuation | The parent's disclosure, with new claims | The parent's filing date | Pursue different or broader claims while the parent is pending |
| Divisional | The parent's disclosure, with claims to an invention restricted out of the parent | The parent's filing date | Respond to a restriction requirement |
| Continuation-in-part (CIP) | The parent's disclosure plus new matter | The parent's date for claims it supports; the CIP's own date for claims that need the new matter | Add an improvement developed after the parent was filed |
| Non-provisional claiming a provisional | A full application following a US provisional | The provisional's date, if filed within 12 months | Secure an early date before the full application is ready |
Continuations and CIPs
Under 35 U.S.C. § 120, a continuation or CIP gets the benefit of an earlier application's filing date if three conditions hold: it is filed while the earlier application is still pending, it names at least one inventor in common, and the claimed invention is supported by the earlier disclosure. The last condition is where a CIP splits. Claims supported by the parent keep the parent's date; claims supported only by the new matter get the CIP's own filing date. MPEP 201 describes each application type.
Chains can run for many years. A continuation can have its own continuation, and as long as one application in the chain is pending, the owner can still draft new claims on the shared disclosure, within what that disclosure supports.
Divisionals
A divisional arises from a restriction requirement: the examiner finds that the parent claims more than one invention and requires the applicant to elect one. Claims to the others can be pursued in divisional applications. Under 35 U.S.C. § 121, a patent issuing on a divisional cannot be used as a reference against the parent, or the parent against the divisional. The statute ties that protection to the restriction requirement, so a continuation filed by choice does not get it.
Foreign priority and international families
Under 35 U.S.C. § 119(a), a US application can claim priority from a foreign application if it is filed within 12 months of the first foreign filing, the window set by the Paris Convention. Under § 119(e), a US non-provisional can claim the benefit of a US provisional filed within the previous 12 months. Other Paris Convention members apply the same 12-month window, which is how one invention ends up filed in many countries under a single priority date.
Databases group these international filings in two standard ways, both defined by the EPO:
- Simple (DOCDB) family: documents that share exactly the same priorities. In practice, usually one invention filed in several offices.
- Extended (INPADOC) family: documents that share at least one priority, directly or indirectly. It pulls in CIPs, continuations that add priorities and related filings, and it can grow large.
A common approach is to count simple families when you want to count inventions, and to check the extended family when you need to be sure no related document is missed.
A hypothetical example
A company files in Germany on 15 March 2017. It files a US application on 1 March 2018, claiming the German priority. While that US application is pending, it files a continuation in 2021 and a CIP in 2022 that adds a new embodiment.
- Term. Under 35 U.S.C. § 154(a)(2), the term ends 20 years from the filing date of the earliest US non-provisional application whose benefit is claimed under §§ 120, 121 or 365(c). Foreign and provisional priority do not count toward the term (§ 154(a)(3)). So the parent, the continuation and the CIP all measure their 20 years from 1 March 2018, not from the 2017 German date, subject to patent term adjustment.
- The CIP's new claims. Claims that depend on the 2022 new matter get the 2022 filing date for prior-art purposes, yet their term still runs from 2018. They face more prior art than the parent's claims, but they expire at the same time.
- The continuation. Filed three years after the parent, it still expires with the parent, apart from any term adjustment. A late continuation adds claims, not years.
When does a US patent expire? covers term adjustment and the other inputs to an expiry date.
Why families matter
Prior art search
Each family member in another office is examined separately, often with different citations. A search report on a European counterpart can list references the US examiner never cited, and those references are worth testing against the US claims. Searching family members is one of the strategies in Prior-art search beyond keywords.
Freedom to operate
- Term. Because continuations generally expire with the parent, the family's earliest US non-provisional filing date tells you roughly when the whole US chain ends.
- Jurisdictions. Protection exists only where a family member is in force. A US patent is no barrier to selling in Germany; the German member is. List members by country and legal status.
- Pending members. A family with a pending continuation can still produce new claims drafted with your product in view, within the parent's disclosure. A clean review of the issued patents says nothing about claims not yet written, so practitioners usually monitor pending members.
Validity and PTAB history
Related patents usually share a specification and similar claims. A reference that anticipates one member is worth testing against the others, and a PTAB record on one member is relevant reading for the rest. Inter partes review: what a PTAB history tells you explains what to look for in that record.
Valuation
Practitioners usually weigh the number of jurisdictions with live members, the remaining term counted from the earliest US non-provisional, and whether a pending continuation still allows new claims. A single issued patent with no pending relatives is a fixed asset; a family with a live continuation can still be shaped.
Double patenting
Claims in two related US patents that are not patentably distinct can raise double patenting. A common resolution is a terminal disclaimer, which ties the later patent's expiration to the earlier one, so check each family member for one before trusting an expiry date. Divisionals filed after a restriction requirement are protected by the § 121 rule above.
Reading a family in practice
- Start from the patent you care about and pull its US continuity data: parents, children and the status of each.
- Find the earliest US non-provisional in the chain. It sets the term for the whole chain.
- Mark every pending member.
- Pull the simple family and list the foreign members by country and status.
- Check the extended family for related filings the simple family misses.
- Note terminal disclaimers and any PTAB proceedings on any member.
How One Transform uses family data
Prior Art searches run several discovery strategies at once, and patent families in other jurisdictions are one of them, alongside citation chains and the inventors' earlier work. Validity searches examine double-patenting exposure among the other grounds and cite the references and reasoning behind each conclusion.
Next step
Pick a patent you are watching, map its family with the six steps above, then run a Prior Art search that includes its foreign counterparts. Start at onetransform.ai.
This article is general information about patent practice, not legal advice. For advice on a specific matter, consult a registered patent attorney or agent.
