Ten-digit dialing

[1][2][3] The added effort in remembering and dialing longer numbers damaged the popularity of overlay plans,[citation needed] which were introduced as a means to reduce the inconveniences associated with the traditional method of splitting an area.

However, overlay plans have become the primary relief method and ten-digit dialing has become increasingly common in the U.S. and Canada.

However, in metropolitan New York City and Chicago, as well as the entire state of California, the initial "1" is required even for local calls for landline phones located within an overlay complex or with a single NPA that also serves customers with a 988 NXX (see below).

As a result, Fort Knox imposed ten-digit dialing for all off-base numbers when the 270/364 overlay was established in 2014.

[5] A July 2020 order by the Federal Communications Commission required ten-digit dialing of telephone numbers with area codes in the United States that were not overlaid, but had an assignment of the central office prefix 988, conflicting with its designation for the National Suicide Prevention Lifeline by federal law.

As part of Canada's implementation of a national 9-8-8 hotline, the Canadian Radio-television and Telecommunications Commission (CRTC) announced in August 2022 that all remaining Canadian non-overlay areas with seven-digit dialing, most of which use "988" as a central office code under their respective area codes, were required to convert to ten-digit dialing by May 31, 2023.

A partial exception existed for the three northern territories served by area code 867, which was not projected to exhaust until at least 2043; only the Yellowknife area (which contains the 988 exchange) was required to convert, with seven-digit dialing remaining optional elsewhere in the region due in part to unique geographical and cultural considerations.