04 vs 05: Australia's mobile numbers and the new range
Who Called Australia editorial team · Updated: 31/08/2026
Every Australian mobile number starts with 04 — ten digits, no exceptions, from 0400 000 000 to 0499 999 999. That neat fact is written into the numbering plan, and it has one known expiry condition: when 04 fills up, 05opens as the next mobile range. Here's how the mobile numbering space actually works, and what an 05 (or 04-something-unfamiliar) caller ID should make you think today.
How 04 is carved up
The ACMA allocates mobile numbers to carriers in ranges, historically often at 04xx-prefix granularity: 0412 went down the Optus line, 0417, 0418 and 0419carry Telstra's analogue-era heritage, 0411 launched with Vodafone, and newer prefixes like 0480 went to the MVNO wave (the full history). The prefix catalogue shows, for each 04xx block, exactly who holds which slices according to the register — often several carriers sharing one prefix at finer granularity.
Why 05 exists
One hundred million numbers sounds inexhaustible until you count second SIMs, dashcams, smartwatches, eSIM churn and every burner plan ever activated. The numbering plan therefore reserves 05xx xxx xxxas the twin of 04: same length, same rules, doubling the mobile space the day it's needed. The ACMA has also pushed machine-to-machine services toward dedicated IoT numbering, which bought 04 years of headroom. The register — which this site imports daily — will show the first genuine 05 allocations when they happen; until then, our lookup treats 05 numbers as structurally valid but flags that no range is in service.
Reading an unfamiliar mobile caller ID
- 04xx you don't recognise: normal — there are 100 prefixes. Check the lookup: the range holder, plus any community reports, appear in one step.
- 05xx today:treat with suspicion. With no 05 ranges in regular service, it's most likely a spoofed display or an overseas origin dressed up as mobile-like digits.
- +61 4… from overseas: the same Australian mobile in international format — normal for Australians roaming. +61 5…: same scepticism as 05.
- Eleven digits, 02–08 start, or 9-digit "mobiles": not a valid Australian mobile at all; classic sign of a sloppily spoofed display.
Related: which carrier owns which prefix · porting: why the prefix no longer proves the network.
Frequently asked questions
Are 05 mobile numbers in use yet?
Not in regular service. The numbering plan designates 05 as the expansion range for digital mobiles once 04 approaches exhaustion, and the register shows no allocated 05 ranges to date. A caller ID starting 05 today therefore deserves scepticism — check the number's page for reports.
How many 04 numbers are there?
The 04 range holds 100 million possible numbers (0400 0000 00–0499 9999 99). With Australia's population, machine SIMs, and years of churn, allocation pressure is real but not yet critical — the ACMA moved IoT services to their own long-number range partly to relieve it.
Can I tell the network from the prefix?
Only historically. Each 04xx prefix was allocated to a specific carrier — 0412 Optus-line, 0417/0418/0419 Telstra-line, 0411 Vodafone-line, and so on — but since porting arrived in 2001, any individual number may live anywhere. Our prefix pages show the register holder plus that history.
What about 01 numbers — are they mobiles?
01x is a special-services range, not standard mobiles. Its best-known residents are satellite phone services on 0141–0145 — Australian numbers that ring in the outback via satellite, and cost accordingly to call.