The Number Portability Landscape

Number portability — the ability to take your phone number with you when you switch carriers or services — has been regulated in most countries for over two decades. In the US, the FCC mandated local number portability in 1996. In the EU, the Universal Service Directive has required it since 2003.

What many people do not realise is that these regulations cover VoIP numbers as well as traditional landline and mobile numbers in most jurisdictions.

How Number Porting Works

Porting a number involves three parties: you, your current carrier (the "losing carrier"), and the carrier you are moving to (the "gaining carrier").

The standard process:

  1. You initiate a port request with the gaining carrier, providing your current number, account number, and billing address as it appears on your current carrier account
  2. The gaining carrier submits a port order to the losing carrier via the industry's porting database (in the US, this is managed by Number Portability Administration Center)
  3. The losing carrier validates the request (checking that the account details match exactly)
  4. If validated, the port is scheduled — typically within 1–7 business days for simple ports
  5. On the port date, the number transfers and your old service stops receiving calls on that number

During this time, your current service continues to work normally. You do not lose the number at any point — it transfers atomically.

What Can and Cannot Be Ported

Can be ported:

  • US landline numbers to VoIP (and vice versa)
  • US mobile numbers to VoIP (and vice versa)
  • UK geographic numbers (01/02 prefixes) to VoIP
  • Most EU geographic numbers
  • Some toll-free numbers (subject to carrier support)

Cannot (or are difficult to) port:

  • Numbers in some countries with limited porting regulations (parts of Africa, some Asian markets)
  • Numbers tied to services (e.g., a number that comes with a bundled broadband package)
  • Some premium rate numbers

The Timeline Reality

Officially, simple domestic ports in the US complete within one business day. In practice:

  • Simple ports (same geographic region): 1–3 business days
  • Complex ports (different geographic region, or porting from a large carrier with manual processes): 5–10 business days
  • International ports (e.g., porting a UK number to a US-based VoIP provider): Often not possible — international number portability is generally only available within a single country

The most common cause of port delays is mismatched account details. Your name, address, and account number must match your current carrier's records exactly — even minor discrepancies (apartment abbreviations, name order) cause the losing carrier to reject the validation and restart the clock.

Porting Mobile Numbers to VoIP

This is a common scenario for people cutting their mobile plan and replacing calls with VoIP. A few practical notes:

Your mobile number can be ported to a VoIP provider. After porting, the number becomes a VoIP number — it will no longer receive SMS messages unless your VoIP provider supports SMS on ported numbers. This is a significant consideration: banking two-factor authentication and many other services rely on SMS to your mobile number.

Before porting, audit which services use your mobile number for 2FA and migrate them to an authenticator app or alternative number first.

Voxa and Number Portability

Voxa is primarily an outbound calling service — the focus is making calls to real telephone numbers, not hosting a virtual number for inbound calls. Voxa does not currently offer inbound DID numbers or number porting.

If your requirement is outbound calling cheaply and without a monthly subscription, Voxa is the right tool. If you need an inbound virtual number that can receive calls (and optionally port your existing number to it), you want a hosted VoIP service with DID support.

Many users combine both: a hosted VoIP service holds their inbound virtual number for receiving calls, while Voxa handles all outbound calling at lower per-minute rates than the hosted VoIP provider charges.

The Bottom Line

Number portability works well for domestic ports in mature markets (US, UK, EU). International portability is rarely available. The main failure mode is mismatched account details causing validation rejections — always verify your account information with your current carrier before initiating a port.

If you are primarily concerned with making outbound international calls cheaply, number portability is not relevant to your decision — outbound calling over VoIP does not require any number porting.