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USPTO guide

Restriction requirements and election of species

By , Co-founder, PatentAssist.ai
Updated

A restriction requirement is often the first thing an applicant hears from the USPTO, and it shapes the whole portfolio: which claims get examined now, which wait for a divisional, and which are lost if nobody acts. This guide explains the legal test the examiner has to meet, how to decide between electing with and without traverse, how rejoinder works, when to file the divisional, and how the answer differs in a national stage application, where unity of invention applies instead.

Quick answer

  • Deadline: 2 months when there is no action on the merits, extendable to 6 months with fees (MPEP 710.02(b), 37 CFR 1.136(a)).
  • You must elect: every reply has to elect one group or species, even if you disagree (37 CFR 1.143).
  • Traverse with reasons: a general objection counts as no traverse and forfeits the 1.144 petition (MPEP 818.01(a), 818.01(c)).
  • Plan for rejoinder: process claims that require every limitation of the elected product can come back in once the product is allowable (MPEP 821.04(b)).
  • National stage is different: 371 applications are judged on unity of invention under 37 CFR 1.475, not on independence, distinctness and burden.

The legal basis: 35 U.S.C. 121

35 U.S.C. 121 lets the Director require an application to be restricted to one invention "if two or more independent and distinct inventions are claimed in one application." The same section gives the non-elected invention two protections: a divisional that meets section 120 keeps the parent's filing date, and a patent from the restricted application cannot be used as a reference against a divisional filed before that patent issues. The last sentence matters in litigation: a patent cannot be invalidated because the USPTO should have restricted it and did not.

The rules split the practice in two. 37 CFR 1.142 covers restriction between inventions; it is "normally made before any action on the merits" but may be made at any time before final action. 37 CFR 1.146 covers election of species, where a generic claim covers several patentably distinct species and the examiner asks you to pick one to search if the generic claim turns out not to be allowable.

What the examiner has to show

MPEP 803 sets two criteria, and a proper requirement needs both: (A) the inventions are independent or distinct as claimed, and (B) there would be a serious search and/or examination burden if restriction were not required. If everything can be searched and examined without serious burden, the examiner "must examine them on the merits, even though they include claims to independent or distinct inventions." An express admission that the inventions are obvious over each other also defeats restriction.

For burden, MPEP 808.02 accepts three showings for search: separate classification, a separate status in the art when classified together, or a different field of search, such as different classes or different search queries. Examination burden can instead rest on non-prior-art issues, for example a section 101 or 112(a) question that affects one group and not the other. Where classification and field of search are the same, the MPEP says "no reasons exist for dividing."

How distinctness is argued for each pairing

Distinctness tests in MPEP 806 by type of related inventions
Claimed together When the examiner can call them distinct
Combination and subcombination MPEP 806.05(c) Distinct if the combination as claimed does not require the particulars of the subcombination for patentability, and the subcombination has utility by itself or in other combinations.
Subcombinations usable together MPEP 806.05(d) Distinct if they do not overlap in scope, are not obvious variants, and at least one has a separate use.
Process and apparatus for its practice MPEP 806.05(e) Distinct if the process can be practiced by another materially different apparatus or by hand, or the apparatus can be used for a materially different process.
Process of making and product made MPEP 806.05(f) Distinct if the process as claimed is not an obvious process of making the product and can make another materially different product, or the product can be made by another materially different process.
Product and process of using MPEP 806.05(h) Distinct if the process of using can be practiced with another materially different product, or the product can be used in a materially different process.
Genus and species, or mutually exclusive species MPEP 806.04 An election of species, not a restriction between inventions: you pick one species for search, and the generic claim is examined with it.

The examiner must give reasons or examples, such as a materially different apparatus that could carry out the process, but usually does not need to cite documents. That is where most good traversals start: an example that is not materially different, or a "different field of search" that would in practice be the same search.

Your reply: the deadline and the election

A restriction or election requirement with no action on the merits sets a 2-month shortened statutory period (MPEP 710.02(b)). Extensions under 37 CFR 1.136(a) cost $235, $690, $1,590 and $2,495 for one to four months at the standard rate, with small entities paying 40% and micro entities 20% of those amounts (USPTO fee schedule). The reply can never run past 6 months from the action. Because the period starts at 2 months, a fourth-month extension is usable here, which it is not after a normal 3-month action.

Simple requirements often arrive by phone first. Under MPEP 812.01, the examiner may call the attorney or agent of record, explain the groups and ask for an oral election, generally with a second call within about 3 working days. You can decline and ask for a written requirement. If you do elect by phone, you must affirm it in the reply to the next action, so decide on traverse before the call back, not during it.

Three rules govern every written reply:

  • You must elect. A complete reply includes an election even when you traverse, and the examiner will not elect for you (37 CFR 1.143, MPEP 818.01(b)).
  • List the claims that read on the election. Identify every claim, including generic and linking claims, that covers the elected group or species. An election of species also needs the claims that read on that species.
  • Answer anything else in the action. If a rejection or objection came with the requirement, you must address it too (MPEP 818.01).

Election becomes fixed once the elected claims get an action on the merits. Claims you add later to a different invention are withdrawn, because the invention first examined is treated as elected by original presentation (MPEP 818.02(a)). This applies in any RCE too, so a request for continued examination is not a way to switch inventions.

Traverse or not: the decision table

Options in reply to a USPTO restriction requirement
Option Use it when What follows
Elect without traverse The groups really are different inventions and you are happy to pursue them separately. Fastest. You give up any later petition under 37 CFR 1.144. Non-elected claims are withdrawn and can go into a divisional.
Elect with traverse The examiner has not shown a serious search or examination burden, or the groups are obvious variants of each other. Requires specific reasons (MPEP 818.01(a)). The requirement is reconsidered, and if repeated and made final you keep the right to petition, no later than the notice of appeal.
Elect and argue a linking claim is allowable A generic or linking claim ties the groups together and you expect it to be allowed. This is not a traverse (MPEP 818.01(d)). If the linking claim is allowed the restriction must be withdrawn; if not, you have conceded the restriction is proper.
Elect, then shape claims for rejoinder You elect the product and still want process claims in the same patent. Process claims that depend from or require all the limitations of the elected product can be rejoined once the product is allowable (MPEP 821.04(b)).
Elect and file a divisional early The non-elected group matters commercially and cannot be rejoined. Starts examination of the second group sooner, with the 35 U.S.C. 121 shield against nonstatutory double patenting, at the cost of a second set of filing fees.

A traverse is a request for reconsideration that must "distinctly and specifically" point out the errors (MPEP 818.01(a)). "Applicant elects Group I with traverse" and nothing more is treated as an election without traverse. Good grounds are concrete: the groups share a classification and the examiner has given no different search strategy; the materially different product the examiner suggests is not actually made by the claimed process; or the species are obvious variants, in which case say so expressly, accepting that the admission can be used against you on obviousness.

A traverse buys a reconsidered requirement, not a fast reversal. If the examiner repeats the requirement and makes it final, the next action also examines the elected claims (37 CFR 1.143). You can then petition the Director under 37 CFR 1.144. The petition can wait until final action on or allowance of the elected claims, but must be filed no later than the notice of appeal. Restriction is petitionable, not appealable: the Patent Trial and Appeal Board will not review it in an ex parte appeal.

Rejoinder: getting withdrawn claims back

When the elected claims are ready for allowance, the examiner reconsiders the restriction and looks at rejoinder (MPEP 821.04). A withdrawn claim is eligible only if it depends from or otherwise requires all the limitations of an allowable claim. In a product and process split where you elected the product, every claim to the non-elected process must meet that test before the process group is rejoined (MPEP 821.04(b)). The MPEP warns that failing to amend non-elected claims to require the elected invention "may result in a loss of the right to rejoinder."

Rejoined claims are fully examined under sections 101, 102, 103 and 112, and the restriction between the rejoined groups is withdrawn. That has a cost: once the restriction is withdrawn, the 121 shield no longer protects a divisional covering the same ground, and a double patenting rejection can follow (MPEP 821.04, citing In re Ziegler). If you would rather keep the process for a divisional, cancel the process claims before rejoinder; the examiner then leaves the restriction in place to preserve your rights under section 121.

Worked example

An application claims a coated stent (claims 1 to 10), a method of making it (claims 11 to 15) and a method of treating a patient by implanting it (claims 16 to 20). The examiner restricts into three groups under MPEP 806.05(f) and 806.05(h), saying the stent could be made by a materially different spraying process and used in a different procedure. You elect Group I, the stent, without traverse, because the burden showing is solid. In the same reply you amend claims 11 and 16 to recite "the stent of claim 1." When claim 1 is allowed, the method claims qualify for rejoinder and the patent can issue with all three groups, with no divisional fees. Had you left claim 11 reciting a generic "drug-eluting implant," it would not require every limitation of claim 1 and would stay withdrawn.

Divisional strategy

A divisional must be filed while the parent is still pending, which means before it issues or is abandoned, to claim its filing date under section 120. It is a new application with its own filing, search and examination fees: $350, $770 and $880 at the standard rate, $2,000 in total before any excess claim or size fees (USPTO patent fees). If it is filed more than six years after the earliest date whose benefit it claims, the continuing application fee under 37 CFR 1.17(w) applies: $2,700 standard after six years and $4,000 after nine. In long families, that alone is a reason not to leave divisionals to the last minute.

The double patenting shield in section 121 is narrow. MPEP 804.01 lists where it does not apply. Three matter most in practice:

  • Applications you file voluntarily, without a restriction requirement. To get the benefit, the claims must have been entered, restricted and removed from the earlier application.
  • Continuations and continuations-in-part. The Federal Circuit held in Pfizer v. Teva (2008) that the protection "is limited to divisional applications," and later cases refused to let patentees relabel a CIP after the fact.
  • Divisional claims that drift across the line of the restriction and claim what was examined in the parent.

Timing is a business decision. Filing the divisional soon after the election gets the second group into the examination queue early, which helps where a competitor's product reads on it. Waiting lets the parent's prosecution history settle the claim language and the prior art first. Either way, docket the parent's allowance: once the issue fee is paid, the window to file closes on the issue date. If speed matters, a divisional can carry its own Track One request from filing; a request in the parent does not carry over.

Unity of invention in 371 national stage cases

If your US case is the national stage of a PCT application, the examiner applies unity of invention under 37 CFR 1.475 and 1.499, not the independent-and-distinct test. MPEP 1893.03(d) reminds examiners of this and requires them to list the groups and explain the unique special technical feature of each. The examiner may raise lack of unity even if the International Searching Authority did not.

Restriction practice compared with unity of invention
Restriction (111(a)) Unity of invention (371)
Which applications Applications filed under 35 U.S.C. 111(a), including bypass continuations of a PCT application National stage applications under 35 U.S.C. 371
Legal test Inventions are independent or distinct, and examining them together would be a serious burden (MPEP 803) Inventions share a special technical feature that makes a contribution over the prior art (37 CFR 1.475(a))
Role of search burden Required. Separate classification, separate status in the art or a different field of search (MPEP 808.02) Not part of the test. The examiner must identify the special technical feature of each group (MPEP 1893.03(d))
Product, process of making and use Often restricted three ways where the process of making is distinct from the product (37 CFR 1.141(b)) Allowed together if the process is specially adapted to make the product and the use is a use of that product (37 CFR 1.475(b))
Review Traverse, then petition under 37 CFR 1.144 The same: 37 CFR 1.499 points to 1.143 and 1.144

Two practical consequences follow. First, a lack of unity objection is answered on the prior art: if the feature the groups share is new and inventive, it is a special technical feature and unity exists. "The examiner has not shown a search burden" is not an argument in a 371 case. Second, the choice of route changes the test. A bypass continuation filed under 111(a) that claims the PCT application is examined under restriction practice even though its claims are the same (MPEP 1893.03(d)). Product, process and use claims that a national stage keeps together under 1.475(b) may be split three ways in the bypass case.

European practice uses the same unity standard as the PCT. If the EPO, as International Searching Authority, charged additional search fees for lack of unity in your PCT application, read its reasoning before the US national stage; it often predicts the US groups. See our guide to the European patent application for how the EPO handles unity and divisionals on its side.

Drafting to avoid a costly restriction

Most restrictions are predictable from the claim set. Writing method claims that recite the claimed product, rather than a looser version of it, keeps them eligible for rejoinder. A strong generic claim with species in dependent form follows 37 CFR 1.141(a), which allows a reasonable number of species in one application where there is an allowable generic claim. And keeping the core feature in every independent claim gives you a special technical feature to point to in a national stage. The claim structure principles are covered in how to write patent claims.

A restriction is not the end of examination, only the start. The first action on the merits usually follows within months; see how to respond to a USPTO office action for the rejections that come next.

Build the claim set before the examiner splits it

PatentAssist.ai drafts claims and specifications in USPTO format, and you can direct the claim structure: a generic independent claim, species in dependent claims, and method claims that recite the claimed product so they stay eligible for rejoinder. Its prior-art search covers USPTO, EPO and Indian records, which helps you judge whether a shared feature is really new before you argue unity. It does not prepare replies to US office actions; that work stays with you or your practitioner.

Try drafting free for 7 days Search US prior art

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Restriction requirements: frequently asked questions

What is a restriction requirement?

It is an office action telling you that your claims cover two or more independent or distinct inventions and that you must pick one to be examined in this application (35 U.S.C. 121, 37 CFR 1.142). It usually comes before any action on the merits. The claims you do not elect are withdrawn, and you can pursue them in a divisional application.

How long do I have to respond to a restriction requirement?

A restriction or election of species requirement with no action on the merits sets a 2-month shortened period (MPEP 710.02(b)). You can extend it month by month under 37 CFR 1.136(a), up to 6 months from the action. At the standard rate a first-month extension costs $235, a second $690 and a third $1,590.

Should I elect with or without traverse?

Traverse only when you have a specific reason the requirement is wrong, such as no real search burden or groups that are obvious variants of each other. A traverse must point out the errors distinctly; a bare statement that you traverse is treated as an election without traverse (MPEP 818.01(a)). Only a traversed requirement can later be petitioned under 37 CFR 1.144.

What is rejoinder?

Rejoinder is the examiner withdrawing a restriction between an allowable elected invention and a non-elected one, then examining the non-elected claims (MPEP 821.04). A withdrawn claim qualifies only if it depends from or otherwise requires all the limitations of an allowable claim, so keep process claims written to require the elected product.

Can I appeal a restriction requirement to the PTAB?

No. A restriction requirement is reviewed by petition to the Director under 37 CFR 1.144, not by appeal. You must have traversed it, it must have been made final, and the petition must be filed no later than the notice of appeal.

Does a divisional application protect me from double patenting?

Yes, within limits. The third sentence of 35 U.S.C. 121 stops a patent from the restricted application being used as a reference against a divisional filed before that patent issues. The Federal Circuit has held that the shield covers divisionals only, not continuations (Pfizer v. Teva, cited in MPEP 804.01), and the divisional's claims must stay within the restricted-out group.

Sources: 35 U.S.C. 121; 37 CFR 1.141, 1.142, 1.143, 1.144, 1.146, 1.475 and 1.499 (eCFR, current to October 22, 2026); MPEP (Ninth Edition, Revision 01.2024) sections 710.02(b), 803, 804.01, 806, 808.02, 812.01, 818, 821.04 and 1893.03(d); USPTO fee schedule (effective January 19, 2025, revised August 14, 2026). This guide is general information, not legal advice. Have a registered patent attorney or agent review your reply.