Your guide to voice over IP (VoIP)

Find out more about making calls over the internet using Voice over Internet Protocol

What is VoIP?

Voice over Internet Protocol (sometimes referred to as an IP phone) uses the internet to make and receive calls. Unlike a traditional telephone it doesn’t use the telephone network, which routes calls across copper cables connected by telephone exchanges.

BT Business VoIP services include our cloud-based systems: BT Cloud Phone, BT Cloud Voice, and BT One Phone; and our on-premises systems: Avaya IP Office and MiVoice Business.

How does VoIP work?

When you make a call, the VoIP software converts the analogue audio signals into digital data, which it transmits over the public internet or your private IP network. You can make calls from your computer or IP phone to another computer, landlines, and mobiles.

The call quality is the same as landlines. You’ll get the same level of clarity and, depending on your system set-up, call quality may be even better

Although the technology behind VoIP is obviously clever stuff, it’s really easy to use. It’s just the same as using a regular phone so you don’t need to worry about having any special techie skills.

What do you need to run VoIP?

The essential things you’ll need are a fast internet connection, VoIP software and an IP phone, or a VoIP phone system. 

Internet connection

The amount of bandwidth you need depends on how much data your business uses and how many people will be on the phone at the same time.

Surprisingly, a VoIP call only uses a fraction of your broadband's capacity so you may not even need fibre broadband to make VoIP work.

To give you an idea: BT Cloud Phone, which is designed for smaller businesses, can comfortably support up to 4 people on the phone at the same time. And that's with just our standard BT Business broadband.

You don't need to worry about this, though. We won’t place any orders until we've talked it through with you. 

IP phone and software 

At its most basic, you’ll need a VoIP phone or a phone with a VoIP adapter, and VoIP software.

For anything more than a single user, you’ll be better off with one of our VoIP phone systems: BT Cloud Phone, BT One Phone, or BT Cloud Voice.


With enhanced 4G now available across most UK towns and cities, possibilities are opening up for VoIP in the mobile market. This is an exciting prospect for any business that has people working away from the office because mobile VoIP calls would be cheaper than calls made over the mobile network.

What can VoIP offer my business?

There’s more to VoIP services than just being able to have a conversation on the phone.


Spend less with VoIP

  • No maintenance costs (compared to a traditional on-premises phone system)
  • There’s only one network to manage (you’ll get your voice and data over the same internet connection so you don’t need your old phone network)
  • Easy to add more ‘phone lines’ (because the ‘lines’ are virtual, you don’t need an engineer out to install new cabling)
  • Reduce travel costs by using web conferencing (instead of holding face-to-face meetings)

Do more with VoIP

  • Mobile device integration (you can divert your office phone to your mobile)
  • Call management features like call forwarding, routing and transfer, voicemail, and three-way calling
  • Audio conferencing
  • Video conferencing
  • Call monitoring and call recording
  • CRM integration (integrate your phone system with your CRM database)
  • An online management portal makes managing the system easy and convenient
  • Virtual geographic numbers so your business can give the impression of being local even if it isn’t

Be flexible with VoIP

  • Employees can hold virtual meetings at the drop of a hat
  • Remote working is easier with VoIP systems
  • Employees can share data and communicate over Instant Messenger
  • If you move you can take your VoIP phone number with you wherever you go (unlike with a traditional landline number, which is tied to your telephone exchange area)

VoIP in a nutshell

Voice over Internet Protocol, or VoIP, is a great way for smaller businesses to make and receive calls over the internet.

If your business has up to four users, all you’ll need to make VoIP calls is:

  • Standard BT Business broadband
  • A VoIP phone or a phone with a VoIP adapter
  • VoIP software

Larger businesses will require:

  • Fast BT Business fibre broadband
  • A VoIP phone system

If your business is growing, adding extra lines is easy and inexpensive. And if you’re moving premises, you don’t need to change your phone numbers as they’re not tied to the local exchange.


Related products