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Patent Filing: Validity and Timing Considerations

You have a new technical idea.

When will you be ready to draft a patent specification?

When will it be appropriate to file an initial application at the Patent Office?

Are there any potential issues with filing an application early and making a follow-up application later?

This Briefing sets out some of the factors to consider in addressing such questions.


You need, first of all, to consider the legal requirements for a valid patent to be granted.

A patent specification comprises two parts: the “description” and the “claims”. The claims are numbered sentences at the end of the specification. For a patent to be valid the invention as defined in the claims must be new and inventive.  Every embodiment of the invention encompassed by the claims must meet these requirements.

For most countries in the world, the date at which the claims must be new and inventive is the date on which a patent application was originally filed at a Patent Office. At this “filing date”, none of the embodiments encompassed by the claims must have been made available to the public or previously disclosed in a patent application. The embodiments must also not be obvious over anything that has been made available to the public at that date.

Everything made available to the public is referred to as the “prior art”. It is essential that you do not disclose your invention to anyone, other than under a signed non-disclosure agreement, before your patent application is filed.  If you do disclose your invention without confidentiality, it becomes part of the prior art.

There is a further validity requirement. The patent specification must provide sufficient information to enable a “skilled” reader to carry out all of the embodiments within the claims. Failure to pass this test is called “insufficiency”.

The Dilemma: When to File?

Considering when to file in the light of validity requirements can pose a dilemma. On the one hand, you may be keen to file your patent application as soon as possible, because with every day that passes more information becomes available to the public. You may be concerned in case one of your competitors beats you to a filing date. On the other hand, you are continually developing your technology and the longer you delay filing the more complete your patent description can be.

The dilemma can be particularly acute in the case of on-going R&D. When do you pause and file patent applications on the inventions made so far? Getting it wrong is known, rather picturesquely, as “self-collision”: you file too early, through fear that your all-too-active competition is working on the same area, and you later find that some critical piece of technical information was missing or incomplete. Perhaps you had not realised exactly what it was that made the invention work, or what distinguished it from the prior art. As your R&D progresses, the missing information is discovered and you file a further patent application around it. It turns out that the first patent application is invalid because the description is insufficient, or because the desired wording for the claims is not present, and the second application is invalid because the invention is obvious over the first application or over a public disclosure you made following your first filing.

How to Avoid Problems

Problems such as filing too early, filing too late or causing a collision between your own patent applications are best avoided through having a clear patent strategy and conducting careful and frequent reviews of your R&D and patenting activities. A key aspect of such a strategy should be to avoid any unnecessary publication of your technology. In other words, do not add to the prior art unless and until you must do so. The usual rule is that you should file a patent application before you disclose an invention to a customer or a supplier, and from this it is often assumed that after filing you are free to disclose. In some situations, however, you may find it useful still to keep the invention confidential by continuing to have non-disclosure agreements signed.  An example of such a situation is where feedback from your customer is likely to cause some redesign of your product, or at least some change of emphasis in the claims.  Of course a confidentiality obligation typically covers only an initial review or trial period and will not usually survive commercial sales to an end user.

The technical level and direction of inventions that are being made in your field need to be monitored with reference to the aims of your own patent filing programme. You will then be better able to judge what sort of detail is likely to be added to the prior art by new competitor filings, and whether they are likely to be aimed at the same problems that you are addressing. You will also know what scope of protection you must obtain if your filings are to be useful to you.

If there is not much activity in the same area by competitors attempting to solve the same problems, you can afford to take more time and enhance the quality and scope of your patent descriptions. If your commercial focus is speculative, you are unlikely to file as soon as you will if you need patent protection for a very specifically designed product of your own.

Prior Art and Publication

However much you try to restrict publication of your technology in order to avoid creating prior art that may later trip you up, you cannot prevent your products becoming prior art when they are released. You also cannot prevent your patent applications being published by the Patent Offices.

It is worth noting the dates on which publication of any relevant ideas will occur and considering whether you have made, or could yet make, any further inventions that would be rendered obvious by these forthcoming publications. You may need to consider filing new patent applications before the otherwise damaging publications occur.

Patent applications in most countries are published automatically by the Patent Offices eighteen months after the original filing date. It should be part of your routine patenting practice to review cases in good time before the eighteen-month date to determine whether any additional patent applications should be filed.