In order to simplify the patent application procedure between countries that are signatory to the Patent Cooperation Treaty (“PCT”), when a PCT international application that has designated the country in which the applicant wishes to apply is submitted to a receiving office (usually, the Patent Office), the date on which the PCT international application is submitted can be recognized as the filing date in each PCT member state.

A PCT international application is not a one-time application for a worldwide patent. Even if an international application is filed, the examination of whether or not a patent is to be granted in each designated country should be determined on the national level. Once the international filing date has been recognized, it should go through the verification stage (i.e., an international search stage and/or an international preliminary examination stage) and the translation thereof should be submitted to each designated country for examination in each country. The PCT has a fixed period for each stage, and applicants and agents must be careful not to miss any periods.

• When an international application is received, the receiving office conducts a formality examination as to whether the submitted document is appropriate or not.
• The International Searching Authority (“ISA”) reviews prior art search and patentability and prepares the results thereof as an International Search Report (“ISR”) and a written opinion (within three (3) months of receipt of the search copy by the ISA or within nine (9) months of the priority date, whichever time limit expires later, and usually around sixteen (16) months from the priority date), to notify the applicant and the International Bureau (“IB”).
• The IB makes international publications of all international applications and international search reports after the expiration of eighteen (18) months from the priority date.
• If a demand for an international preliminary examination, a separate optional procedure, is filed in respect to an international application (usually within twenty two (22) months from the priority date), the International Preliminary Examination Authority (“IPEA”) conducts a preliminary examination on patentability and reports the results thereof as "International Preliminary Examination Report (“IPER”) on Patentability," and notifies the applicant (usually within twenty eight (28) months from the priority date).
• The applicant enters the national phase (usually within thirty (30) months of the priority date) to pay fees for the translation of the international application, fees for the national phase, and the like to the country in which he/she wants to obtain a patent, on the basis of the above report, and the like. In Korea, the national phase should be entered within thirty one (31) months of the priority date.