VoIP vs landline for business: UK 2027 guide

For most UK businesses, VoIP is now the practical long-term choice over a traditional PSTN or ISDN landline. Specifically, BT plans to retire its Public Switched Telephone Network by 31 January 2027, so organisations still using legacy services need a tested migration plan.

That does not mean business landline numbers will disappear. A company can keep a fixed telephone number and landline-style service, but calls will normally travel through digital technology such as Voice over Internet Protocol.

This guide compares VoIP with traditional landlines, explains what the 2027 switchover changes and helps businesses choose the right digital voice setup.

VoIP vs landline: what is the difference?

In simple terms, a traditional business landline carries calls through the circuit-switched Public Switched Telephone Network, or PSTN. ISDN is a digital service that also operates within that older network environment.

By contrast, VoIP converts speech into digital data and sends it across an IP network. Depending on the service, employees can make and receive calls through desk phones, computers or mobile apps.

Consequently, the comparison is becoming less about choosing between two permanent alternatives. Instead, UK businesses need to decide how they will replace legacy PSTN and ISDN services with a suitable digital option.

Are UK landlines being switched off?

At present, the old PSTN technology is being retired, but fixed telephone services and familiar landline numbers will continue. Ofcom explains that customers who want to keep a landline service will move to digital technology, commonly called VoIP, Digital Voice or an all-IP service.

BT plans to retire its PSTN by 31 January 2027. Other providers using BT’s network must work to the same timetable, while providers with their own networks may follow a similar but separate plan.

However, the UK Government notes that not every analogue phone service will necessarily disappear on the same date. Businesses should confirm the timetable for each service with the company that bills and supports it.

Therefore, for current information, see Ofcom’s digital landline guidance and the UK Government’s switchover guidance.

What is a traditional business landline?

Historically, a traditional landline uses a dedicated physical telephone line connected to the PSTN. Historically, businesses used analogue lines, ISDN2 or ISDN30 services to connect individual phones or an on-site PBX.

Although these services were dependable and familiar, but the underlying infrastructure is ageing and increasingly difficult to maintain. In addition, many legacy products are already under stop-sell restrictions, so organisations cannot treat them as a long-term option.

Even so, a physical copper cable may still enter the building after migration. What changes is the service carried across the network, not necessarily every cable on the same day.

What is business VoIP?

In short, VoIP stands for Voice over Internet Protocol. It carries voice calls as data over an IP connection rather than a traditional circuit-switched telephone service.

For example, hosted business VoIP places the main phone-system functions in a provider’s cloud platform. Users connect through compatible desk phones, softphones or mobile apps, while authorised administrators manage numbers and call routing through a portal.

Alternatively, another option is SIP trunking, which connects a compatible on-site or private phone system to the public telephone network over IP. The right choice depends on existing equipment, sites, internal skills and the level of control required.

VoIP vs landline comparison

Consideration	Traditional PSTN/ISDN landline	Business VoIP
Long-term UK availability	Legacy network is being retired	Designed for the digital network
Connection	Dedicated circuit-switched line	IP network and suitable connectivity
Working locations	Usually tied to a premises or PBX	Can support approved office, home and mobile devices
Scaling	May require lines, ports and installation	Users and licences can often be changed through a portal
Features	Depends on the PBX and network service	Often includes routing, apps, reporting and integrations
Power cuts	Some corded analogue phones may retain line power	Local routers, switches and phones need backup power
Administration	May require on-site configuration	Usually managed centrally
Business continuity	Often linked to one premises	Can use alternative devices or routes when planned

Of course, these are broad differences rather than promises. The exact result depends on the provider, network, equipment and service design.

What are the advantages of VoIP?

Flexible working

A hosted service links a user to an account instead of one physical socket. Therefore, employees may use the business number from approved devices in the office, at home or while travelling.

As a result, this flexibility supports hybrid and field-based teams without forcing colleagues to publish personal mobile numbers. Historic UK workplace commentary from the original article is retained here, although each organisation should design around its current working pattern.

Easier scaling

In most cases, adding a VoIP user is normally an administrative task rather than a new line installation. Likewise, licences may be reduced when a seasonal team becomes smaller.

Nevertheless, check minimum commitments, device lead times and broadband capacity. A hundred new licences will not help if the network cannot support the expected simultaneous calls.

Central management

For instance, an authorised administrator can usually manage users, call groups, opening hours and routing from one portal. As a result, several sites can follow consistent rules without configuring every phone separately.

Strong access controls are essential. Use individual administrator accounts, multi-factor authentication where available and the lowest permission level each person needs.

Business application integrations

In addition, some phone systems connect with customer relationship management, helpdesk or productivity software. A compatible CRM phone integration might open the correct customer record when a call arrives or allow click-to-dial from a contact.

However, an integration does not simply copy an entire customer database into the phone system. Before enabling it, check the supported version, user permissions, data flows and behaviour during an outage.

Call recording and analytics

For example, where there is a defined purpose and compliant process, call recording can support training, quality checks or evidence of a transaction. A UK organisation must choose and document an appropriate lawful basis, be transparent, control access and set a justified retention period.

Call analysis may show busy periods, missed calls and other patterns. However, figures need context: a short call is not automatically successful, and a long call is not necessarily inefficient.

Professional call handling

An auto attendant can provide a short menu and direct callers to the right team. Opening-hour rules, ring groups and voicemail can also give customers a clear next step when someone is unavailable.

Above all, keep menus brief and test the journey as a caller. Complex automation can create more effort than it removes.

Business continuity options

Moreover, because a hosted service is not limited to one office socket, calls can often be redirected to another site, mobile app or agreed number. This can help during a building closure or local connection fault.

Even so, the plan still depends on power, devices, connectivity and the provider’s platform. Test every alternative route before it is needed.

What are the disadvantages of VoIP?

Internet dependency

First, VoIP needs a suitable IP connection. Congestion, packet loss, jitter or a broadband failure can affect calls.

Therefore, a business should assess bandwidth, local networks, Wi-Fi and peak simultaneous calls. Critical locations may also need a second connection or mobile failover.

Power dependency

Likewise, routers, network switches and IP phones generally require mains power. Therefore, digital calls may stop in a local power cut unless the equipment and connectivity have suitable backup.

Plan around the complete call path. Backup power for one handset is not useful if the router or switch has already stopped.

Security risks

For instance, weak credentials, exposed administrator accounts and unrestricted international calling can create fraud and data risks. Use strong passwords, multi-factor authentication, limited permissions, updates and active monitoring.

Migration work

In addition, number porting, network changes, device setup and employee training need careful sequencing. In addition, alarms, lift phones, fax machines and payment terminals may require separate replacement services.

Variable provider quality

Support, resilience and security differ between suppliers. Do not choose from a headline licence price alone; compare service targets, escalation routes and the full contract.

Are there any advantages to a traditional landline?

Historically, legacy landlines have been familiar and, in some cases, independent of a customer’s broadband connection. Certain corded analogue telephones could also work during a local power cut because the line supplied power.

Even so, those characteristics matter when designing the replacement. However, they do not make PSTN or ISDN a sustainable new choice because the network is being retired.

The useful question is not “How can we keep the old service forever?” It is “Which digital service and resilience measures will preserve the functions we still need?”

Will a digital landline work like the old one?

Generally, for ordinary calls, the experience may feel similar. A telephone may plug into a router, adaptor or provider-supplied hub rather than the traditional wall socket.

However, there are important differences:

• local equipment normally needs mains power
• the service may depend on a broadband or managed IP connection
• some older handsets and devices may be incompatible
• emergency-location information must be managed correctly
• alarms and other non-voice equipment require testing

A landline-only digital service may be available for people who do not want general internet access. The provider should explain the product and migration process.

VoIP and emergency calls in the UK

Importantly, business VoIP can support UK emergency calls to 999 and 112. The organisation and provider must ensure that service and location details are handled correctly, especially when users work from different sites.

Therefore, ask how the platform manages registered locations, remote users and address changes. Employees should also understand any limitation and what alternative to use if power or connectivity fails.

Never rely on US guidance about 911 for a UK business phone system.

What happens during a power cut?

In the past, some traditional analogue telephones could continue using power supplied through the line. Most digital voice equipment cannot do that without local backup.

First, identify which calls and users are critical. Then consider an uninterruptible power supply, backup connectivity, mobile phones or pre-agreed diversion.

Ofcom requires providers to offer an appropriate solution to customers who depend on their landline and cannot otherwise contact the emergency services during a power cut. Business continuity needs may go further, so agree them in the service design.

Can a business keep its existing number?

In most cases, eligible UK telephone numbers can be ported to a new provider. Accurate account details and a complete number inventory are essential.

Do not cancel the old service before the new provider confirms the porting process. Early cancellation can delay the transfer or put numbers at risk.

Record direct-dial numbers, published numbers, fax numbers and any number linked to an alarm or other device.

What else may be connected to a landline?

Above all, a business phone migration must look beyond desk telephones. Common dependencies include:

• intruder and fire-alarm signalling
• lift emergency phones
• door-entry and intercom systems
• payment and franking machines
• fax machines and modems
• telecare or social-alarm equipment
• building-management and telemetry devices
• out-of-hours and emergency phones

Ask the equipment manufacturer, maintainer and communications provider to confirm compatibility. An adaptor does not guarantee that every analogue device will work reliably.

The original article linked to this earlier PSTN and ISDN switchover overview. Use current provider, Ofcom and UK Government information for live decisions.

Is VoIP cheaper than a landline?

In many cases, it can simplify costs and reduce some installation or expansion expenses, but it is not automatically cheaper in every case.

Compare the total cost of:

• user licences and optional features
• desk phones, headsets and conference devices
• broadband and local network improvements
• backup power and connectivity
• installation, number porting and training
• support, maintenance and contract changes
• calls outside an allowance

A credible proposal should separate one-off and monthly charges and explain what happens when user numbers change.

What broadband does business VoIP need?

In practice, the required capacity depends on the codec, overhead and maximum simultaneous calls. Moreover, voice quality relies on low latency, low jitter and minimal packet loss as well as raw speed.

Upload performance matters because calls travel in both directions. Wi-Fi coverage, routers, switches and traffic prioritisation also affect the result.

Ask the provider to assess the complete network rather than relying on one consumer speed test. Wayv’s earlier business broadband information is retained from the original article.

How to choose between business VoIP services

Finally, since legacy PSTN and ISDN products are being retired, compare digital options against the same written requirements. Ask each provider:

• How will you assess our connectivity and local network?
• What support hours, targets and escalation routes apply?
• Who owns our telephone numbers and manages porting?
• How are emergency calls and user locations handled?
• What security controls and administrator permissions are available?
• What happens during a power or broadband failure?
• Which devices and integrations are supported?
• What training is included?
• What are the full costs, contract term and exit arrangements?

Moreover, involve the employees who answer and transfer calls. A demonstration or pilot can expose awkward workflows before the business commits.

Wayv also outlines phone-system choices by company size.

Business phone migration checklist

• List every site, line, number, contract and provider.
• Identify phones, alarms, lifts, fax machines, payment devices and other connected equipment.
• Record users, locations and peak simultaneous calls.
• Assess broadband, Wi-Fi, switches and routers.
• Define power and connectivity resilience.
• Compare hosted VoIP, SIP trunking and specialist replacement services.
• Agree the number-porting sequence without cancelling early.
• Configure emergency locations, permissions and call routes.
• Pilot the system and test every important journey.
• Train users and administrators.
• Decommission legacy services only after written sign-off.
• Review bills and performance after launch.

VoIP vs landline FAQs

Will business landlines stop working in January 2027?

BT plans to retire its PSTN by 31 January 2027, but businesses should confirm the migration date for each service with their provider. Fixed numbers and landline-style services will continue digitally.

Is a digital landline the same as VoIP?

Digital landline services generally use internet protocol technology to carry calls. Providers may call the service VoIP, Digital Voice or all-IP telephony.

Does a business have to replace every desk phone?

Not necessarily. Some phones may work with a compatible adaptor or service, while others need replacement. Confirm support and functionality with the provider.

Can VoIP work without broadband?

VoIP requires an IP connection, but a provider may supply a managed connection or digital landline-only product rather than a general internet package.

Is VoIP reliable enough for business?

Yes, when it uses suitable connectivity, network design, support and resilience. The service should be built around the organisation’s call and continuity needs.

Does VoIP work in a power cut?

Only if the required router, switches, phones and connectivity have suitable backup. Plan for the whole service rather than one device.

Which is better for a UK business: VoIP or a traditional landline?

VoIP is the viable long-term option for most businesses because the traditional PSTN and ISDN network is being retired. The important choice is which digital voice service and resilience plan best fit the organisation.

The verdict: migrate thoughtfully, not simply quickly

Ultimately, traditional PSTN and ISDN landlines are approaching retirement, so keeping them indefinitely is not a realistic strategy. Business VoIP offers flexible access, central control and modern call features, but it must be supported by suitable connectivity, security and continuity planning.

To discuss a requirements-led migration, visit Wayv’s business VoIP page.