Patent Cooperation Treaty (PCT) is an international patent law treaty, concluded in 1970 with more than 145 contracting states or countries. PCT provides a unified procedure for filing patent applications for an invention simultaneously in a large number of countries by filing a single "international" patent application instead of filing several separate national or regional patent applications. The granting of patents remains under control of the national or regional patent offices in what is called the "national phase".

PCT filing procedure: One can file an application under the PCT directly or within the 12-month period provided from the filing date of first application, valid in all contracting states of the PCT and therefore, simpler, easier and more cost-effective than both, direct or Parisroute filings.

Stages of PCT filing procedure:

Filing: One can file an international application with a national or regional patent office or WIPO, complying with the PCT formality requirements.

International search: International Searching Authority (ISA) (one of the world's major patent offices) identifies the published patent documents and technical literature ("prior art") which may have an influence on whether the invention is patentable, and establishes a written opinion on invention's potential patentability.

International publication: As soon as possible after the expiration of 18 months from the earliest filing date, the content of the international application is disclosed to the world.

Supplementary international search (optional): On request, a second ISA identifies published documents which may not have been found by the first ISA which carried out the main search because of the diversity of prior art in different languages and different technical fields.

International preliminary examination (optional): On request, one of the ISAs carries out an additional patentability analysis, usually on an amended version of your application.

National phase: After the end of the PCT procedure, usually at 30 or 31 months from the earliest filing date of initial application, from which the priority is claimed, one can start to pursue the grant of your patents directly before the national (or regional) patent offices of the countries in which one chooses to obtain the patent right.

Other than assisting applicants in seeking patent protection internationally for their inventions, PCT helps patent offices with their patent granting decisions, and facilitates public access to a wealth of technical information relating to those inventions.