Ten-digit dialing: why local calls need the area code
Published
Why many local calls now need the area code: overlays, and the 988 crisis line change of 2021 and 2022. What seven-digit, ten-digit and 1+10 dialing each mean.
Seven digits, ten digits, or 1+10
Seven-digit dialing means dialing only the prefix and line number for a local call, leaving off the area code. It still works in some places that have a single area code.
Ten-digit dialing means the area code plus those seven digits, even for a call next door. 1+10 means a 1 in front of the ten digits. Long-distance calls are usually dialed 1+10, and some states use 1+10 for local calls too. Chicago's 312 is one place where local calls are dialed 1+10.
Sources: NANPA: 2025 annual report (new area codes, overlays and dialing plans); NANPA planning letter PL-390: 872 to overlay the 312 and 773 area codes (Illinois)
Why overlays need the area code
Where an overlay puts two or more area codes in the same place, the same seven digits can exist under each code. The phone network needs the area code to know which one you mean, so seven-digit local calls stop working when an overlay starts.
FCC rules also require ten-digit dialing in every overlay, so that numbers in the old code and the new code are dialed the same way and neither group of customers has an easier number to call.
The 988 change
In July 2020 the FCC chose 988 as the three-digit number for the national suicide prevention and mental health crisis line. In some area codes that still allowed seven-digit dialing, 988 was also the prefix of ordinary local numbers. A switch receiving 988 could not tell whether the caller wanted the crisis line or a local number that starts with 988.
The FCC's order required ten-digit local dialing in every area code that both allowed seven-digit dialing and used 988 as a local prefix. With the area code dialed first, a local number that begins with 988 can no longer be taken for the crisis line.
Sources: FCC 20-100: report and order designating 988 and requiring ten-digit dialing; NANPA: abbreviated dialing codes, including 988; NANPA planning letter PL-556: transition to ten-digit dialing for 988
When the change happened
NANPA set the schedule. In the affected area codes, ten-digit dialing became optional on April 24, 2021, and the mandatory dialing date was October 24, 2021. Phone companies had until July 15, 2022 to finish enforcing it, and 988 began reaching the crisis line on July 16, 2022.
Dialing 988 on its own still reaches the crisis line, and 911 is still three digits.
Sources: NANPA planning letter PL-556: transition to ten-digit dialing for 988; NANPA: abbreviated dialing codes, including 988; NANPA: area code relief frequently asked questions
What to update
Anything set to dial seven digits stops reaching local numbers once ten digits are required. That includes alarm systems, speed dial lists, call forwarding settings, office phone systems and fax machines. Printed numbers that leave off the area code need updating too.
A business in an overlay area should show every number with its area code, on its website, its signs and its ads.