What Are VoIP Numbers And How Do They Work?

As telephone technology evolves, more businesses are adopting VoIP (Voice over Internet Protocol) phone systems and using VoIP numbers instead of relying on traditional landlines. The chances are that you’ve already received calls from VoIP numbers without realising it, as the call experience is no different for recipients.

As the 2025 Big Switch-Off nears (when UK landlines will officially be switched off), many businesses are making the transition to alternative phone lines. VoIP is a great solution that offers several added benefits, which we’ll also cover in the article.

But what exactly are VoIP numbers and how do they work? Read on to learn everything you need to know about this important telecommunications development.

What Does a VoIP Number Look Like?

You likely wouldn’t be able to tell the difference between a VoIP number and a landline number. When displayed on phones or caller ID systems, VoIP numbers are totally indistinguishable from traditional landline or mobile numbers. From the caller’s point of view, there is no visible difference when placing or receiving a call to a VoIP number, as they just appear as regular 10-digit phone numbers. There is no visible difference between calling a landline number vs. a VoIP number from the caller’s perspective.

VoIP numbers also share the same national and local dialling formats as landline numbers. They have three-digit area codes and seven-digit local number components that conform to Ofcom’s telephony numbering plan for the UK.

Types of VoIP Numbers

Local VoIP Numbers	Toll-Free VoIP Numbers	Vanity VoIP Numbers
Local VoIP numbers are tied to a specific geographic area and resemble a standard landline number from that area. A local VoIP number uses an area code and prefix from your region. This allows customers to easily recognize that your business is located in their area. Local numbers build trust and are ideal for businesses focused on serving customers nearby.	Toll-free VoIP numbers can be dialled from anywhere in the UK without long-distance or international calling charges. Numbers typically start with 0800 or 0808 prefixes. Toll-free numbers help project professionalism and encourage calls from potential customers across the country. They make your business seem larger and more established.	Vanity VoIP numbers spell out a word or business name when translated into numbers on a phone keypad. These customized numbers are easy to remember and help reinforce brand identity. Instead of a random string of digits, your number contains letters matching your company name, product, or service. Vanity numbers are excellent for advertising and making an impression.

How Do VoIP Numbers Work?

A VoIP phone number works just like a regular phone number, except it is connected to a VoIP network instead of a traditional landline or mobile network. When someone dials your VoIP number, it routes the call to your business phone system over the Internet rather than traditional Public Switched Telephone Network (PSTN) infrastructure. VoIP converts analogue voice signals into digital data packets that can be transmitted over IP networks.

Here is a quick play-by-play of what happens when somebody tries to reach you on your VoIP number:

The caller dials your unique VoIP phone number from their device
The call is routed from the regular phone network to your VoIP provider data centre via a media gateway
Your VoIP provider converts analogue voice signals into compressed digital packets
Digital packets traverse the internet over VoIP provider’s SIP trunk to your business system
Your VoIP phone system converts packets back into analogue signal
Call rings appropriate office or mobile phone to connect the call

While it sounds like a rather complicated process, the end result is a completely identical calling experience to that of a landline or mobile phone.

▶ Read more: A Guide to Business Number Porting

Substantial cost savings – No need to pay for expensive physical hardware or calling plans from telecom providers
Improved mobility – Make and receive calls remotely via desktop or mobile apps
Enhanced functionality – Sophisticated call handling features and intelligent call routing
Easy scalability – Simply add new lines and numbers as your business grows
Reliable connectivity – You’re less likely to miss important calls thanks to a safety net of failover options and a 99.9%+ uptime guarantee

How To Tell If a Phone Number Is a VoIP Number

Does a number that called or texted you belong to a VoIP provider?

There are a couple of quick checks you can perform:

Try calling the number back – VoIP numbers will typically connect you directly without going through a standard operator
Look up the number on a reliable, UK-based reverse phone lookup website – The results should indicate if the number is registered to a VoIP provider or virtual phone number company
Check if the number has previously been registered as a landline or mobile number – If not, it likely belongs to an internet-based phone provider.

By investigating the number or trying to call it back, you should be able to confirm if it is a VoIP phone number. This can provide useful context and help determine if an incoming call, text message, or other communication is of a business or personal nature.

Differences Between VoIP Numbers and Landline Numbers

There are several key differences between traditional landline phone numbers and modern VoIP numbers. One of the benefits of VoIP systems is that they easily outperform landlines for a variety of reasons.

Location Independence

Traditional landline numbers are tied to specific copper phone cables and physical hardware at homes or businesses. This has historically meant that setting up a business phone system was a costly investment that required a fixed office location and several office phones. However, VoIP numbers are virtual and live in the cloud. This means that organisations can dynamically add, change, or move numbers without on-site visits.

Cost

In addition to the upfront costs of maintaining an office space and hardware, a landline phone system requires expensive switched infrastructure from telecom providers and is usually on a fixed contract. Alternatively, VoIP works with existing internet connectivity with no added costs for physical call routing hardware or office phones. Instead, you’ll just pay a monthly contract fee for the VoIP system.

Moreover, calling international numbers is often cheaper with VoIP thanks to calls being routed over the internet.

Portability

Conventional landlines only work from the phone devices they are wired to within a location. In a modern workplace, where remote working is increasingly prevalent, this makes landlines an outdated option. VoIP numbers break free of devices and can be used across smartphones, desktop computers, and tablets – virtually anywhere with internet access. Calls to VoIP numbers can ring all your configured endpoints simultaneously or sequentially.

Functionality

Landlines have limited built-in features beyond calling, holding, transferring, and screening messages. On top of maintaining reliable lines of communication, VoIP numbers support advanced features like AI call agent assistance, intelligent call routing tools, real-time analytics, integration with CRM and marketing tools, messaging platforms, mobile apps, and auto-attendant services.

▶ Read more: How to Get a Business Phone Number

How Do You Get a VoIP Phone Number?

While we have highlighted how VoIP phone systems can streamline and upscale your business communications, you may be wondering how to get your own VoIP phone number.

For your business to migrate to VoIP, the first port of call is to sign up for a VoIP phone system with one of the top business VoIP providers in the UK. It’s important to consider the needs of your business and identify a provider that meets your requirements.

For example, look at whether your phone system is used for external calls to clients or internal calls among your team – this will inform the sorts of features that are a priority for your business. Also, consider your business size. Start-ups in the growth stage may prioritise economic options, whereas developed businesses may look at a complex, enterprise-level system.

To minimise disruption, most leading providers also make it simple to port over existing phone numbers previously used for traditional landlines. This means you won’t miss any important customer calls during the switch.

In addition to supplying your company with VoIP numbers, many business VoIP providers include unlimited local and national calling packages. This allows employees to make calls within the UK free of charge, regardless of where contacts are located.

Conclusion

With so many benefits, including smarter call management features, greater location flexibility, premium call quality, and substantial cost savings, it’s no wonder VoIP phone numbers are experiencing a sharp uptake in the UK.

As landline networks phase out in favour of internet-based solutions, VoIP numbers are fast becoming the new standard. Businesses should seriously consider switching over to reliable business VoIP solutions with fresh VoIP numbers or porting existing landlines over to future-proof communications before the 2025 Big Switch-Off deadline.

For more support throughout the switching process, consult our complete guide on how to set up your own VoIP phone system for everything you need to know for a seamless transition.