National Phase

The stage of a patent application under the Patent Cooperation Treaty (PCT) which is performed separately before the national or regional patent offices covering each territory in which patent protection is desired. 

The start of this stage is commonly referred to as "entering the national phase" and occurs at approximately 30 months after the first patent application for an invention has been filed (although this varies from country to country).  This marks a significant milestone, being the point at which it is necessary to decide which territories patent protection will be sought in and at which the costs of continuing to pursue the patent application increase significantly (owing the need to pay official fees and take various procedural steps separately in each of those territories, as well as the need to engage local representatives in each territory).