In general, a port of entry (POE) is a place where one may lawfully enter a country. It typically has a staff of people who check passports and visas and inspect luggage to assure that contraband is not imported. International airports are usually ports of entry, as are road and rail crossings on a land border. Seaports can be used as ports of entry only if a dedicated customs presence is posted there. The choice of whether to become a port of entry is up to the civil authority controlling the port.
The formal definition of a port of entry in the United States is something entirely different. According to the Code of Federal Regulations, "the terms 'port' and 'port of entry' incorporate the geographical area under the jurisdiction of a port director." In other words, a port of entry may encompass an area that includes several border crossings, as well as some air and sea ports. This also means that not every border crossing is a port of entry. There are two reasons for this:
In some countries, immigration procedures are carried out by the armed forces rather than specific immigration officers. However in most, the levying of duty on imports is still carried out by customs officers. Immigration clearance at in some ports of entry have automated sections open to the country's own residents or citizens, such as the E-Channel found in Hong Kong and Macau, and Global Entry found at some airports in the United States.
On some international borders, the concept of a port of entry does not exist. Travelers may cross the border wherever and whenever convenient, for example within the Schengen Area. In some cases this may be restricted to citizens of specific countries and to travelers who are not carrying goods over the customs limits; others may only cross the border at a designated border crossing during its opening times.