Trunk prefix

A trunk prefix is a digit sequence to be dialed before the telephone number to initiate a telephone call for the purpose of selecting an appropriate telecommunications circuit by which the call is routed.

In most countries making a domestic telephone call requires the dialing of a single digit preceding any necessary area codes and subscriber numbers. In most countries, such as Australia, Germany and the United Kingdom, the trunk prefix is 0. In the North American Numbering Plan it is 1. When the same telephone number is called from another country, the national trunk prefix is not dialed, instead for international calls an international trunk access code is typically required. Many countries use the sequence 00, but in the United States and the NANP areas it is 011.

Example

Assume a call is to be made to someone in the Australian state of Queensland with the number 3333 3333.

A caller from outside Australia would dial the international access international call prefix of the originating country, then dial the country calling code (in this case 61), then dial the area code (in this case 7), and then the local number. A caller in the UK dials 00 61 7 3333 3333, while a caller in the USA dials 011 61 7 3333 3333.

Calling interstate (e.g. from Western Australia), a caller does not dial an international access number or country code, but dial the trunk prefix 0 then the area code, followed by the telephone number: 0 7 3333 3333 Calling from within Queensland one simply dials the telephone number: 3333 3333.

When conducting business (e.g., on business cards or stationery, etc.), the number should be written as +61 7 3333 3333 and include only the digits that must be dialed from abroad. The plus sign is used to indicate the country code is following. It has become common practice to write the number with the trunk prefix in parentheses, for example: +61 (0) 7 3333 3333. However, someone calling this number from the United States may mistake the trunk code for a single-digit area code, as NANP area codes are often written in parentheses, dial all the digits and result in a failed call.^[1] ITU-T Recommendation E.123 states that parentheses should not be used in the international notation.

Countries using trunk prefixes

The number next to the country in the list below denotes the country's national trunk prefix.

Americas

Asia

Europe

Oceania

Africa

Countries no longer using a national trunk prefix

• Czech Republic
• Denmark
• Estonia
• Greece
• Italy - Leading 0 is dialled both within and from outside Italy (just because 0 is now part of the number and not the trunk code)
• Latvia
• Luxembourg
• Malta
• Monaco
• Norway
• Poland
• Portugal
• San Marino - Leading 0 is dialled both within and from outside San Marino (just because 0 is now part of the number and not the trunk code)
• Spain
• Vatican City - Leading 0 is dialled both within and from outside Vatican City (just because 0 is now part of the number and not the trunk code)

See also

• Subscriber trunk dialling

References

• Glossary - World Telephone Numbering Guide.