A trunk prefix is a digit sequence to be dialed before a "Local" telephone number to initiate a telephone call for the purpose of selecting an appropriate longer distant telecommunications circuit by which the call is to be routed.
In most countries the making of a domestic "out-of-area" or "Trunk" telephone call requires the dialing of a Trunk Access code (usually, a single digit) followed by an Area Code before dialing the customer's "local area" number. In many countries, such as Australia, Germany and the United Kingdom, the Trunk Access code is 0. In the North American Numbering Plan the Trunk Access code is 1.
When such a customer's "local" telephone number is called from another country, the National Trunk Access code is, of course, not needed. Instead, for international calls, a National International Access Code is required, followed by the "Country Code" of the country concerned, (usually followed by an "Area Code" - in all but small countries and Italy), followed by the "local" telephone number. Many countries use the sequence 00 for their International Access Code. However, in the member states of the NANP, such as the US and Canada, the code used is 011.
It should be noted that for GSM Mobile (Cell) phones the International Access Code of any and all countries may be replaced by the symbol "+".
A caller from outside Australia must dial the International Call Prefix of the originating country, plus the Country Calling Code (in the case of Australia - 61), plus the Area Code (in this case - 7), and then the local number. Therefore a caller in the UK must dial 00 61 7 3333 3333, while a caller in the USA must dial 011 61 7 3333 3333.
Calling inter-area (within Australia) (e.g. from Western Australia - Area Code "8"), a caller need not dial an international access number or a Country Code. However, the caller must at least dial the Australian trunk access code (0) followed by the area code (7) and then the "local" telephone number: 0 7 3333 3333 Calling from within the Queensland (7) "area", a caller need only dial the telephone number: 3333 3333.
However, because the worlds telephone systems are "intelligent" enough to "know" from where the call has been originated, to where the call is directed and as to how it is to be charged, if the full International number is used, then this full International number may be dialed from any telephone anywhere. This is particularly important for users of Mobile (Cell) 'phones. Such users are strongly advised to store all numbers in their 'phones in the form of "+ (Country Code) (Area Code) (Local Number)", no matter where they live. Storing numbers in this manner will ensure that they can connect to any such stored number from any Area or Country in the world without any further consideration when they travel to any destination in the world.
(The fees charged by any telephone provider in an international circumstance is not related to the storage of numbers in this manner and is irrelevant to this article.)
When conducting business, e.g., for display on business cards or stationery, the number should be written as +61 7 3333 3333, and include only the digits that must be dialed from internationally. The plus sign is used to indicate that that an international trunk access code is first dialed and, therefore, a "Country Code" then follows. It has become common (but incorrect) 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. 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.
- Albania - 0
- Austria - 0
- Belarus - 8
- Belgium - 0
- Bosnia and Herzegovina - 0
- Bulgaria - 0
- Croatia - 0
- Cyprus - 0
- Finland - 0
- France - 0
- Georgia - 0
- Germany - 0
- Hungary - 06
- Ireland - 0
- Kosovo - 0
- Lithuania - 8 (planned to be 0 later)
- Macedonia - 0
- Moldova - 0
- Montenegro - 0
- The Netherlands - 0
- Romania - 0
- Russia - 8
- Serbia - 0
- Slovakia - 0
- Slovenia - 0
- Sweden - 0
- Switzerland - 0
- Turkey - 0
- Ukraine - 0
- United Kingdom - 0
Countries no longer using a national trunk prefix
- Czech Republic
- Italy - Leading 0 is dialled both within and from outside Italy (because 0 is now part of the number and not the trunk code)
- San Marino - Leading 0 is dialled both within and from outside San Marino (because 0 is now part of the number and not the trunk code)
- Vatican City - Leading 0 is dialled both within and from outside Vatican City (because 0 is now part of the number and not the trunk code)
- "How to Dial International Phone Numbers". Tech-faq.com. Retrieved 2012-06-13.
- Glossary - World Telephone Numbering Guide.