The first difference between US and foreign patent laws is that the US provides a one year grace period between the time an applicant discloses his invention to the public via newsletters, blogs, youtube, etc. and the time the applicant files a patent. In foreign patent prosecution, if an applicant discloses his invention to the public he is barred from obtaining patent protection for his invention. Therefore, before considering filing a foreign patent it is important to consider if there has been any public disclosure of your invention.
The second difference between US and foreign patent prosecution is that in US patent prosecution all utility applications are automatically examined in the order that they are received. In some foreign countries, once an application is filed, the applicant must elect for the patent to be examined. Therefore, in foreign countries an application may be pending for several years without being examined. Countries that implement these types of systems will typically charge a maintenance fee to keep the application pending during the time between filing and examination that is lower than an examination fee.
The third difference (until March 16, 2013) is that the US utilizes a “first to invent system” to be establish a priority date for an invention, rather than the “first to file system” of other countries. Currently for US patent application US applicants may file an application after another applicant and be granted a patent if they can prove they were the first to invent the invention. Conversely, in foreign countries the first inventor to file an application is presumed to invent the invention and may be granted a patent even if they were not the first to actually invent the idea.
The fourth difference between US and foreign patent prosecution relates to formality issues. Each country has different patentability standards that it adheres to. For example, in the US patent applications may be filed with 20 total claims, 3 being independent with no additional charge, whereas in European prosecution 15 total claims may be filed with only 2 being independent without additional charges. Each country may also have different variations on claim structure, response dates, and allowed amendments to claims. For example, in the US claims may be amended during prosecution as long as there is literal or inferred support for the amendment in a figure or specification, while to amend claims during prosecution of a Chinese patent application the claims must be amended with the actual words in the specification (literal support).