What is a VoIP number? Fixed vs non-fixed, and why apps turn it down

What is a VoIP number?

A VoIP number is a phone number assigned to a Voice over IP service rather than to a SIM card or a physical line. It looks like any other number, and anyone can dial it from a normal phone. Only the route differs: the call reaches you over the internet, in an app, a desk phone or a browser tab.

US rules call the service behind it interconnected VoIP: two-way voice over broadband that can both receive calls from and place calls to the ordinary phone network ^[9]. That link is what separates a VoIP number from a username in a calling app.

You meet VoIP numbers in three places: home phone lines from providers such as Comcast and Vonage ^[1], business phone systems such as Sonetel ^[10], and personal numbers from services like Google Voice, TextNow and TwinPhone ^[11][12][8]. How the call then reaches a tab is covered in WebRTC, SIP and the phone network.

Fixed vs non-fixed VoIP numbers

A fixed VoIP number is tied to a physical device, such as a home phone line from Comcast or Vonage. A non-fixed VoIP number is obtained online, needs no device and works wherever you sign in. Line-type lookups, which businesses can run before sending texts, report the two as separate types ^[1], and FCC rules treat them differently for 911 ^[13].

A service that runs such a lookup sees the line type and the carrier name ^[1], whatever the area code. Carrier Wi-Fi Calling is a different thing: it is a setting of the SIM line on your phone ^[15], so the number stays mobile. I set the two side by side in Wi-Fi Calling vs VoIP.

Some personal VoIP services have no emergency calling at all; the free Google Voice plan and TwinPhone both exclude it ^[16][17]. I check which services reach 911, 112 or 999 in my guide to emergency calls from a browser.

Why do banks and apps reject VoIP numbers?

Because they use your number to prove who you are, not only to reach you. Capital One wants a US mobile number registered to your name, and Login.gov checks the number against public and proprietary records ^[2][5]. A non-fixed VoIP number can be opened online, sometimes with no documents ^[8], so it says little about its holder. That last step is my reading; none of these pages spells it out.

Login.gov is the telling case: it accepts plain landlines but not Google Voice-type numbers ^[5], so the objection is weaker proof of identity, not a missing SIM. Even TwinPhone, which sponsors this site and sells numbers, warns that Telegram, banks and payment apps often refuse virtual numbers ^[8].

How to tell whether a number is VoIP

Not from the digits: a US VoIP number has the same +1 and ten digits as a mobile or landline ^[21]. The answer comes from the provider that issued it, or from a line-type lookup such as Twilio's, which a business can run before sending a code ^[1]. For a number you hold, three questions usually settle it.

1. Did you get it from an app or a website? Then it is almost certainly non-fixed VoIP.
2. Does it ring through a box at home from a cable or internet provider? That is fixed VoIP.
3. Is it on a SIM card from a mobile carrier? Then it is mobile, even when the phone calls over Wi-Fi Calling ^[15].

Where to get a VoIP number and what it costs

In the US, Google Voice and TextNow give personal numbers for free, and TextNow also covers Canada; the other two services I checked charge for numbers. All four hand out numbers online with no device, which is how Twilio defines non-fixed VoIP ^[1], so none is a safe bet for bank codes. The real differences are the countries covered and what sign-up asks of you.

Sonetel's terms limit use to business purposes ^[29].

Calls to a TwinPhone number ring in a browser tab or the iPhone app and cost $0.02 a minute from your calling balance ^[30]. The trade-offs: no free tier or trial credit ^[17], a $10 minimum top-up ^[31], no sending texts ^[14], and no emergency calls ^[17].

If what you want is a second line for everyday calls, my guide to a second number compares the options.

What to do when a service rejects your VoIP number

Don't try to get around the check; give the service what it asks for. That usually means a mobile number in your name, or an option that needs no phone number at all, such as an email address. These steps follow the bank and government pages I read.

1. Check the service's help page for accepted number types; all six above publish theirs.
2. Look for a route without a phone number: Bank of America lets you enroll an email address for Zelle instead ^[4].
3. Use a mobile number registered to your name, as Capital One asks; Login.gov suggests another number associated with your name ^[2][5].
4. With no other number, contact the service. Login.gov's advice is to ask the agency what you can do instead ^[5].

Frequently asked questions

Related reading

• Guides

  How to get a second phone number: eSIM, free apps or a number in your browser

  I compared the ways to get a second phone number without a second SIM: an eSIM line, Google Voice, TextNow and rented numbers that ring in a browser tab.

• Guides

  Calling 911 from a computer: what works, what is blocked and what to use instead

  Can you call 911 from a computer? I checked which browser and VoIP services connect 911, 112 or 999, what the rules require, and what to use instead.