Editing Telephone numbering plan (section)

==Subscriber dialing procedures==
While a telephone numbering plan specifies the digit sequence assigned to each telephone or wire line, establishing the network addresses needed for routing calls, numbering plan administrators may define certain dialing procedures for placing calls. This may include the dialing of additional prefixes necessary for administrative or technical reasons, or it may permit short code sequences for convenience or speed of service, such as in cases of emergency. The body of dialing procedures of a numbering plan administration is often called a [[dial plan]].

A dial plan establishes the expected sequence of digits dialed on subscriber premises equipment, such as telephones, in private branch exchange (PBX) systems, or in other telephone switches to effect access to the telephone networks for the routing of telephone calls, or to effect or activate specific service features by the local telephone company, such as 311 or 411 service.

===Variable-length dialing===
Within the North American Numbering Plan (NANP), the administration defines standard and permissive dialing procedures, specifying the number of mandatory digits to be dialed for local calls within a single numbering plan area (NPA), as well as alternate, optional sequences, such as adding the prefix 1 before the telephone number.

Despite the closed numbering plan in the NANP, different dialing procedures exist in many of the territories for local and long-distance telephone calls. This means that to call another number within the same city or area, callers need to dial only a subset of the full telephone number. For example, in the NANP, only the seven-digit number may need to be dialed, but for calls outside the local numbering plan area, the full number including the area code is required. In these situations, [[ITU-T]] Recommendation [[E.123]] suggests to list the area code in parentheses, signifying that in some cases the area code is optional or may not be required.

Internationally, an area code is typically prefixed by a domestic trunk access code (usually 0) when dialing from inside a country, but must not be dialed when calling from other countries; there are exceptions, such as for [[Telephone numbers in Italy#Numbering plan|Italian land lines]].

To call a number in Sydney, [[Australia]], for example:
* xxxx xxxx (within [[Sydney]] and other locations within [[New South Wales]] and the [[Australian Capital Territory]] - no area code required)
* 02 xxxx xxxx (outside [[New South Wales]] and the [[Australian Capital Territory]], but still within Australia - the area code is required)
* 61 2 xxxx xxxx (outside [[Australia]])

Dialing internationally, the country code must be preceded by the [[international access code]], which is ''00'' in many countries per ITU recommendation. This is indicated in notation when the character ''+'' precedes the area code. Some telephone types, especially mobile phones, allow the + to be entered directly, causing automatic substitution by device or the carrier. In the North American Numbering Plan, the prefix is ''011'' before the destination country code.<ref>{{Cite web | url=https://www.fcc.gov/consumers/guides/international-long-distance-calling-made-simple-tip-sheet |title = International Calling Tip Sheet|date=2011-07-19 |website=fcc.gov}}</ref>

[[New Zealand]] requires the area code to be dialed when calling between two local calling areas.

In California and New York, because of the existence of both overlay area codes (where an area code must be dialed for every call) and non-overlay area codes (where an area code is dialed only for calls outside the subscriber's home area code), "permissive home area code dialing" of 1 + the area code within the same area code, even if no area code is required, has been permitted since the mid-2000s. The manner in which a call is dialed does not affect the billing of the call.  This "permissive home area code dialing" helps maintain uniformity and eliminates confusion given the different types of area code relief that has made California the nation's most "area code" intensive state.

===Full-number dialing===
In small countries or areas, the full telephone number is used for all calls, even in the same area. This has traditionally been the case in small countries and territories where area codes have not been required.  However, there has been a trend in many countries towards making all numbers a standard length, and incorporating the area code into the subscriber's number. This usually makes the use of a trunk code obsolete.
For example, to call someone in Oslo in [[Norway]] before 1992, it was necessary to dial:
* xxx xxx              (within Oslo - no area code required)
* (02) xxx xxx         (within Norway - outside Oslo)
* 47 2 xxx xxx        (outside Norway)

After 1992, this changed to a closed eight-digit numbering plan, e.g.:
* 22xx xxxx     (within Norway - including Oslo)
* 47 22xx xxxx (outside Norway)

However, in other countries, such as [[France]], [[Belgium]], [[Japan]], [[Switzerland]], [[South Africa]] and some parts of North America, the trunk code is retained for domestic calls, whether local or national, e.g.,

* [[Paris]] 01 xx xx xx xx (outside France +33 1 xxxx xxxx)
* [[Brussels]] 02 xxx xxxx (outside Belgium +32 2 xxx xxxx)
* [[Geneva]] 022 xxx xxxx  (outside Switzerland +41 22 xxx xxxx)
* [[Cape Town]] 021 xxx xxxx (outside South Africa +27 21 xxx xxxx)
* [[New York City|New York]] 1 212 xxx xxxx (outside the North American Numbering Plan +1 212 xxx xxxx)
* [[Fukuoka]] 092 xxx xxxx (outside the Japanese Numbering Plan +81 92 xxx xxxx)
* [[India]] "0-10 Digit Number" (outside India +91 XXXXXXXXXX). In India due to the availability of [[Telephone numbers in India|multiple operators]], the metro cities have short codes which range from 2 to 8 digits. 

While some, such as [[Italy]], require the initial zero to be dialed, even for calls from outside the country, e.g.,

* [[Rome]] 06 xxxxxxxx (outside Italy +39 06 xxxxxxxx)

While dialing of full national numbers takes longer than a local number without the area code, the increased use of telephones that can store numbers means that this is of decreasing importance. It also makes it easier to display numbers in the international format, as no trunk code is required—hence a number in [[Prague]], Czech Republic, can now be displayed as:

* 2xx xxx xxx (inside Czech Republic)
* +420 2xx xxx xxx (outside Czech Republic)

as opposed to before September 21, 2002:<ref name="CTO-renumbering2002">{{Cite journal |title=Číslovací plán veřejných telefonních sítí |journal=Telekomunikační Věstník |volume=9/2000 |date=2000-09-25 |publisher=Czech Telecommunication Office |url=http://www.ctu.cz/1/download/cislovaci-plan-verejnych-telefonnich-siti_1114435245.pdf |access-date=2006-10-13 |url-status=dead |archive-url=https://web.archive.org/web/20061101053806/http://www.ctu.cz/1/download/cislovaci-plan-verejnych-telefonnich-siti_1114435245.pdf |archive-date=November 1, 2006 |language=cs}}</ref>

* 02 / xx xx xx xx  (inside Czech Republic)
* +420 2 / xx xx xx xx (outside Czech Republic)