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Glossary · Numbering

What is Exit code?

  • Also called: international access code, idd prefix, international prefix

Reviewed by Sujan ThapaliyaLast updated

Definition

An exit code is the digits dialled to leave your own country's numbering plan before an international number — 011 from North America, 00 across most of Europe. The plus sign in E.164 stands in for whichever exit code applies where the call is placed.
The three STIR/SHAKEN attestation levels, which underpin how exit code behaves in practice: A asserts both that the carrier knows the customer and that the customer may use the calling number, B asserts the customer only, and C asserts neither. A shared number pool can reach B at best, which is why number ownership keeps recurring in these definitions.
Attestation is the backdrop to most caller-ID and deliverability terms, exit code included.

In practice

How exit code actually works

This is why storing numbers with a plus rather than a local exit code matters: a number saved as 011 44 20 7946 0958 works from the United States and fails from everywhere else, while +442079460958 works anywhere.

Mobile handsets translate the plus automatically, which is why saving numbers in international format is the practical advice regardless of where the phone usually is.

A few countries use exit codes other than 00 or 011, and some have carrier-specific variants, which is another argument for the plus.

Exit codes are also the reason click-to-dial links break across borders. A number stored with a local exit code works from the country it was saved in and nowhere else, which is why every contact database should hold the plus form and let the handset translate it.

Worked example

Calling London from New York: 011 44 20 7946 0958. From Paris: 00 44 20 7946 0958. Stored as +44 20 7946 0958, both work.

Exit code: common questions

What is the exit code for the United States?
011, dialled before the country code when calling internationally from a landline. Mobile handsets accept a plus instead, which is more portable.
Can I always use + instead of the exit code?
On mobile networks, yes — the handset substitutes the correct digits. On some landline and PBX systems the exit code is still required.
Why do international calls fail with the right number?
Most often a missing exit code, a trunk prefix left in place, or a PBX that strips the plus. Test the same number stored in E.164 to isolate which.

Sources

  1. Combating Spoofed Robocalls with Caller ID Authentication — Federal Communications CommissionThe STIR/SHAKEN framework, the attestation levels carriers sign calls with, and the mandate requiring providers to authenticate caller ID.
  2. 47 U.S.C. § 227 — Restrictions on the use of telephone equipment — Cornell Legal Information InstituteThe Telephone Consumer Protection Act itself — the consent requirements, calling-hours limits, and private right of action.
  3. ITU-T Recommendation E.164 — The international public telecommunication numbering plan — International Telecommunication UnionThe international number format, the 15-digit maximum, and how country codes and national numbers compose.

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