So you finally got your patent application ready to file and are working on the cover sheet and notice there are multiple lines to list one or more inventors. Who should you list? Will your co-founders be upset if they are left off of the patent? There are very strict rules which must be followed when deciding inventorship on a patent. In fact, getting inventorship wrong and purposely misleading the patent office may result in the invalidation of your entire patent and other penalties.
To determine proper inventorship, you must first understand what your patent claims will be. Patent claims are a summary of the unique aspects of your invention and will define the legal scope of protection which your patent provides. Once the patent claims are defined, each person who can point to one or more claims and say “that was my idea” should be listed as an inventor. Even if a person can only point to one small feature listed in one claim among a large list of claims that person should still be listed as an inventor. There is no minimum amount of inventorship required to be listed on a patent but an inventor must be more than just a pair of hands.
Simply carrying out steps or instructions issued by an inventor does not rise to the level of inventorship required to be listed on a patent. It is quite possible that one person (i.e. a co-founder) may do 99% of the work on a project but unless they contributed to the original ideas claimed in the patent, they should not be listed as an inventor.
Deciding inventorship can be a tricky issue with some 'politics' involved. It is often best to bring in an outside patent attorney or patent agent to explain the legal concept of inventorship to each person involved. In extremely delicate situations where every person wants to be listed on a patent application, you may be able to find a unique contribution from each person and make sure to include each of those contributions in the claims, if you can do this and if those claims are allowed, than each person can be listed on the patent.