Local Number Formats Around the World: What Outbound Teams Need to Know

Why Format Matters for Outbound Caller ID

The goal of displaying a local number is for the prospect to recognize it as local and answer it. That recognition happens in the roughly two seconds between when their phone starts ringing and when they decide to pick up or ignore.

Recognition requires that the number display in the format the prospect expects to see numbers from that region. A German prospect in Berlin expects to see a number starting with 030 (national format) or +49 30 (international format). If they see +4930 (missing a space in the wrong place), 004930 (ITU-T with a 00 trunk prefix), or 0049 30 (another trunk prefix variant), the display is unfamiliar and the recognition benefit is partially or fully lost.

This is not hypothetical. Different SIP carriers, dialers, and terminating carriers handle format translation inconsistently. Building the display format correctly into your origination path matters.

E.164: The Baseline Standard

E.164 is the ITU-T standard format for international phone numbers: plus sign, country code, subscriber number, no spaces or formatting characters. +14155552671 for a US San Francisco number, +442079460290 for a London number.

E.164 is the format used in SIP signaling and in most carrier-to-carrier interfaces. It is the "machine-readable" format. The display format that appears on a recipient's screen depends on how the terminating carrier or handset renders the E.164 number for the local market—usually by stripping the country code and applying national formatting conventions.

For outbound teams, the practical implication is: provision and configure numbers in E.164 in your systems, but verify that the end-to-end path to the terminating carrier produces the expected display format in the target market.

Key Format Variations by Market

United States and Canada. Ten-digit subscriber numbers (area code + seven-digit local number), typically displayed as (415) 555-2671 or 415-555-2671 on US handsets. Country code +1, shared between US, Canada, and several Caribbean nations. Prospects often screen for unfamiliar area codes—geographic matching is a primary answer rate driver. STIR/SHAKEN attestation applies to originating US/CA carriers.

United Kingdom. Numbers vary in length: London 020 + 8 digits (total 11 with leading 0 in national format), mobile 07 + 9 digits, other geographic codes varying in length (e.g., Cardiff 029, Birmingham 0121). National format always has a leading 0 that E.164 removes. A London number 020 7946 0290 in E.164 is +44 20 7946 0290. Prospects see the number rendered by their handset—verify terminating carrier rendering.

Germany. Highly variable number length. Berlin 030 has 8-digit local numbers; smaller cities may have 5-digit local numbers. The Vorwahl (area code) length itself varies: Hamburg is 040, Cologne is 0221. Total number length in national format ranges from 10 to 12+ digits depending on area and number type. Mobile numbers start with 01x. The variability makes format verification more important than in markets with fixed-length numbers.

France. 10 digits total in national format (0 + 9 subscriber digits). Geographic zones indicated by the second digit: 01 Paris, 02 Northwest, 03 Northeast, 04 Southeast, 05 Southwest. Mobile numbers start with 06 or 07. Consistent length makes France format-simpler than Germany.

Australia. Geographic numbers: leading 0 in national format, 8-digit subscriber number (total 10 digits). Area codes: 02 (NSW/ACT), 03 (VIC/TAS), 07 (QLD), 08 (SA/WA/NT). Mobile numbers start with 04 (total 10 digits). In E.164, the leading 0 is removed: +61 2 xxxx xxxx.

Netherlands. Geographic numbers: 10 digits total in national format. Major cities (Amsterdam, Rotterdam) have 010/020 codes. Mobile numbers start with 06. Consistent structure relative to Germany.

Brazil. 11 digits in national format for mobile numbers in many cities (following a 2012 addition of an extra digit). Geographic area codes (DDDs) range from 11 (São Paulo) to 99 (Maranhão). Mobile numbers in most major areas now start with 9 after the DDD. Format mismatches between pre-2012 10-digit records and current 11-digit requirements are a common source of display errors.

Japan. Geographic numbers: 0 + area code + subscriber number, total 10 or 11 digits depending on area. Tokyo numbers: 03-XXXX-XXXX. Mobile numbers start with 090, 080, or 070 (total 11 digits). Japan's character display system may render numbers differently on some handsets.

The Trunk Prefix Problem

Many countries' national-format numbers begin with a "trunk prefix"—a 0 in the UK, Germany, France, Australia, and many others. E.164 omits this trunk prefix, replacing it with the country code.

When SIP signaling passes numbers in E.164 but a downstream component in the path adds back a trunk prefix, you can end up displaying +440207946 (UK number with both the E.164 format and an extra 0 inserted). This produces an unrecognizable display.

Conversely, when a national-format number (with leading 0) is passed through a system expecting E.164 without stripping the trunk prefix, the number can display with a doubled prefix or in a malformed state.

Verify the number format at every stage of your origination stack: dialer configuration, SIP origination carrier, and terminating carrier rendering. The caller ID by country reference documents expected display formats for all 33 markets in UnlimCall's coverage.