Do Restriction Requirements Vary by Technology Center?

By Christopher Holt
July 7, 2013

I have been preparing and processing patent applications for about fourteen years, primarily within the electrical, mechanical and software technologies.  From my perspective, the issuance of restriction requirements seems to be somewhat random and inconsistent.  It is often the case, in fact, that I do not get a restriction requirement when there might be a relatively good reason for one to be issued.

On the other hand, I have always heard that practitioners in the chemical and biotechnological arts suffer from a higher than average issuance of restriction requirements.  I set this week to do a little research to see whether this assumption could be statistically validated using PatentAdvisor Search Tool.

Restriction requirements are governed by MPEP § 806.06 .  In a nutshell, a restriction requirement is to be issued by an examiner where there are multiple distinctly claimed inventions in one patent application and it would be overly burdensome for the examiner to go forward with one application.  For patent prosecutors and their clients, restriction requirements represent a significant cost increase as splitting one patent application into several new applications results in the multiplication of fees and, often, loss of protection due to expense limitations.  The pros and cons probably do depend on the technological context, however.


Claims presented in the chemical and biotechnological arts, as I understand it, are seen as prime targets for restriction requirements because they often include different species within a genus.  MPEP 1.142 does allow for a patent application to link a reasonable number of species to a generic claim. However, many patent prosecutors claim that patent examiners in the chemical and biotechnological arts are very eager to split up this type of claim set.

However, when we review the facts (derived from the PatentAdvisor database); they tell a different story.  The database contains statistics and analysis, including the frequency of restriction requirement issuance, for all art units in the patent office.  Following is a table that shows the commonality of restriction requirements across all art units in four of the major patent office technology centers:

Tech. Center

RRs issued

Patents issued

Average %

MaxArtUnit %

MinArt Unit %



















Mechanical Engineering






This table validates the perception that the biotechnology technology center average issuance of restriction requirements is high.  Interestingly, this tech center also has the art unit with the lowest occurrence of restriction requirements across all art units regardless of tech center.  It is worth noting; however, the art unit in question (Art Unit 1661) is dedicated to plants.

Surprisingly, although the chemical tech center does have a higher average issuance of restriction requirements issued than semiconductor patent applications or mechanical engineering applications, the difference is quite small.  Finally, it is worth noting that the Semiconductors Technology Center includes art units with a higher rate of restriction requirements than any art unit in the Chemical Technology Center (2811 at 60% and 2814 at 50%).

Knowing the frequency of restriction requirements in an art unit before drafting an application can prepare both the prosecutor and the client for potential restriction requirements.  Additionally, knowing the likelihood of restriction requirements in a specific art unit before filing could help suggest alternate strategies, such as postponing disclosure of some species for a divisional application, extending the patent term and potentially avoiding a restriction requirements

The Author

Christopher Holt

Christopher Holt

Warning & Disclaimer: The pages, articles and comments on do not constitute legal advice, nor do they create any attorney-client relationship. The articles published express the personal opinion and views of the author as of the time of publication and should not be attributed to the author’s employer, clients or the sponsors of Read more.

Discuss this

There are currently 2 Comments comments.

  1. George July 8, 2013 9:29 am

    Very interesting post–thanks. I am just wondering whether there is any way in the Patent Advisor database (which I have not used) to screen applications by categories such as continuation or divisional versus an original filing, because of course it might be the case that some of the applications that are not receiving restriction requirements were filed as divisionals following a restriction requirement in the parent application. Another thing that would be interesting to know but might be hard to figure out would be the effect of species elections–I’m in biotech, and we get a ton of these on top of official restriction. Sure, there is supposed to be rejoinder of nonelected species if the generic claim is allowed, but in practice there are multiple species elections and if claims are allowed at all we usually don’t force the issue of rejoinder, so in effect it’s just a further restriction requirement (and you would have to file a new application to pursue the additional species) even though officially it’s called something else and you don’t get the statutory protection against double patenting if you do later pursue those claims. I’m not sure why the PTO handles it this way–I’ve always found the rules confusing, and trying to understand the MPEP sections on restriction requirements is enough to give anyone a headache.

  2. Anon July 11, 2013 5:57 pm

    A question comes to my mind (separate – but related):

    What are the best ways of fighting restriction requirements?

    I am seeing a number of extremely dubious requirements based on ‘difficulty of search’ in child aplllications for which the same excuse was used in a parent application – but the different subclasses were searched anyway in the parent application.

    I would think that a major case like KSR would eviscerate the ‘excuse’ of difficulty to search, because, after all, the Court itself said that patents may be denied if the disparate art fields could be put together like pieces of a jigsaw puzzle.

    It simply strikes me as the Office either NOT doing its job, or trying to inflate its coffers by having multiple applications.