The UK PSTN switch-off deadline is 31 January 2027. After this date, traditional analogue and ISDN services will no longer provide the foundation for business calls, fax machines, alarms, lift phones or other legacy equipment.
The direct replacement is not simply “another phone line”. Most businesses will move to an IP-based service delivered through a suitable internet connection. The main options are hosted VoIP, SIP trunking and digital voice services.
For UK decision-makers, the important issue is selecting the right voice service and ensuring the supporting infrastructure is ready. This includes bandwidth, power, failover, internal cabling, equipment compatibility and ownership of business telephone numbers.
What replaces an analogue business phone line?
Hosted VoIP, SIP trunking or digital voice replaces the analogue line, depending on the existing phone system and operational requirements.
The three main options are:
| Replacement | How it works | Suitable for |
|---|---|---|
| Hosted VoIP | The phone system is delivered from a provider’s hosted platform and accessed over an IP connection. | Businesses modernising legacy telephony, supporting multiple sites or enabling flexible working. |
| SIP trunking | IP voice trunks connect an existing on-premises PBX to the telephone network. | Organisations that want to retain a compatible PBX while replacing ISDN or analogue trunks. |
| Digital voice | A straightforward IP voice service is delivered through a router or connectivity service. | Smaller offices requiring basic calling without a complex phone system. |
The UK Government’s Telecommunications Modernisation Connectivity Timeline confirms that all users of the Openreach PSTN must migrate to new services by 31 January 2027.
The correct choice depends on the number of users, sites, call-handling requirements, existing equipment and the resilience expected by the business.
Is hosted VoIP the best replacement for business phone systems?
Hosted VoIP is usually the most flexible replacement for businesses that want a modern, scalable phone system without retaining a legacy PBX.
A hosted service can support business numbers, call routing, hunt groups, voicemail, auto-attendant functions, call queues and user extensions over an IP connection. It can also support teams across multiple premises, provided the connectivity and network design are suitable.
The commercial benefits include:
- Scalable user and extension management
- Centralised call routing across locations
- Support for hybrid and multi-site teams
- Reduced dependence on on-premises telephone hardware
- Easier relocation when offices change
- Improved continuity when paired with resilient connectivity
Hosted VoIP does not remove the need for engineering discipline. We assess the internet connection, firewall, switching, wireless coverage, internal cabling, power arrangements and failover plan before migration.
Our telecoms and phone systems capability supports structured planning around the complete service rather than treating the phone system as an isolated purchase.
When is SIP trunking the right option?
SIP trunking is appropriate when a business has a compatible existing PBX and wants to replace analogue or ISDN trunks while retaining its established call-handling configuration.
This approach can protect investment in suitable on-premises equipment and reduce the disruption associated with replacing the entire phone system. It requires a detailed compatibility review covering the PBX, licensing, numbering, call capacity, codecs, firewall configuration and provider requirements.
We also review:
- Current ISDN or analogue trunk arrangements
- Number ranges and direct-dial numbers
- Simultaneous call requirements
- Inbound and outbound routing
- Emergency calling arrangements
- Failover behaviour during an internet outage
- PBX support and replacement timescales
SIP trunking is not automatically the lowest-risk route. An ageing PBX may create continued maintenance, security and resilience issues even after the analogue connection has been replaced. A structured comparison between SIP trunking and hosted VoIP provides better long-term investment protection.
What equipment is affected besides the telephone?
Any device that communicates over an analogue line may be affected, even if it is not recognised as a phone.
A line audit should identify every connected device, not just desk phones and reception numbers. The PSTN switch-off can affect:
- Intruder alarm diallers
- Fire alarm signalling equipment
- Lift emergency phones
- Door-entry systems
- Payment terminals using analogue dial-up
- Fax machines
- Modems
- Building management equipment
- Monitoring and telemetry devices
- Legacy broadband services
BT’s guidance on the PSTN switch-off specifically highlights alarms, lift lines, point-of-sale equipment and telecare devices as examples of services that may rely on legacy networks.
The replacement may be IP-based, mobile, cellular or dual-path, depending on the equipment and the required level of protection. The relevant alarm company, lift maintenance provider, payment provider or equipment manufacturer must confirm compatibility and complete end-to-end testing.
Does digital voice require a better internet connection?
Yes. Digital voice depends on the quality, capacity and resilience of the business internet connection.
A phone call may use less bandwidth than video traffic or cloud backups, but voice quality is sensitive to delay, jitter, packet loss and congestion. A connection that appears acceptable for email may deliver poor call quality during busy periods.
Before migration, we assess:
- Peak and average internet utilisation
- Available download and upload capacity
- Latency, jitter and packet loss
- Firewall and router configuration
- Quality-of-service requirements
- Number of simultaneous calls
- Traffic from CCTV, payments and remote access
- Availability of a secondary connection
Our business internet connectivity service covers business broadband, fibre, leased lines, dedicated internet access, dual-WAN and 4G/5G failover.
The connection should be designed around the whole operation. Our guide to business internet connectivity in the UK explains why digital voice, cloud services, payments and CCTV can turn an ordinary internet connection into a business-critical dependency.
What happens to business numbers during migration?
Business numbers can normally be ported to a new digital voice provider, but ownership and porting records must be confirmed before any service is cancelled.
Number loss is one of the most avoidable risks in a telephone migration. The business should document:
- Main published numbers
- Direct-dial numbers
- Geographic and non-geographic numbers
- Number ranges
- Numbers used by alarms or payment equipment
- Current provider and account holder
- Contract and cancellation terms
- Porting status and target date
Do not cancel the existing service before number porting has completed and inbound and outbound calls have been tested. The organisation that owns the service account may also differ from the reseller or installation company, so ownership must be checked early.
A controlled migration includes a porting plan, agreed cutover window, temporary call forwarding where appropriate and a rollback procedure.
Will digital phones work during a power cut?
Not without suitable backup power or an alternative communications path.
Traditional analogue lines could sometimes continue operating during a local power failure because power was supplied from the telephone exchange. IP voice normally depends on the premises’ mains supply, router, network equipment and local access connection.
For business continuity, we recommend reviewing:
- UPS or battery backup for routers and network equipment
- Backup power for critical communications devices
- 4G or 5G failover
- Dual-WAN configuration
- Diverse connectivity routes where justified
- Mobile or dual-path alarm signalling
- Emergency contact procedures
- Documented outage testing
Critical systems should not rely on a single broadband connection and a single mains-powered device. We design resilience around the operational consequences of an outage.
The Cybersecurity section on our services page should also be considered during migration. New voice equipment, routers and remote access paths must be securely configured, maintained and monitored.
Does internal cabling affect the replacement?
Yes. Internal cabling and network layout directly affect the performance and reliability of digital voice.
Hosted VoIP handsets and network-connected voice equipment require reliable Ethernet connectivity, suitable switching and clear separation between user devices and critical infrastructure where the design requires it.
We review:
- Existing Cat 5e or Cat 6 cabling
- Patch-panel condition and labelling
- Switch capacity and power delivery
- Network cabinet organisation
- Voice and data segmentation
- Wireless coverage where mobile voice devices are used
- Handoff location for the internet service
- Cable routes and future expansion requirements
Our article, Structured Cabling for UK Businesses: Why a Tidy Server Rack Saves You Money, explains how organised, documented and fully tested cabling reduces fault-finding time and protects future connectivity upgrades.
What should a business do before 31 January 2027?
Complete a full audit, select the replacement service, confirm connectivity and test every dependent device before the deadline.
A practical migration plan includes:
- Inventory every analogue and ISDN service.
- Record every number and connected device.
- Choose hosted VoIP, SIP trunking or digital voice.
- Review bandwidth, latency, power and failover.
- Confirm number ownership and porting requirements.
- Contact alarm, lift, payment and equipment providers.
- Upgrade cabling, switching or connectivity where required.
- Configure security controls and call-routing requirements.
- Test inbound, outbound, emergency and failover calling.
- Document the finished service and support arrangements.
Our earlier guide, UK PSTN Switch-Off: 10 Steps Businesses Must Take Before 31 January 2027, provides the wider preparation framework.
Frequently asked questions
Is hosted VoIP the same as digital voice?
Hosted VoIP is a type of digital voice service delivered over an IP connection. The exact features, management model and equipment depend on the provider and the selected service.
Can we keep our existing business numbers?
In most cases, numbers can be ported, but the current account ownership, number range and provider arrangements must be verified before migration.
Can we keep our existing PBX?
Possibly. SIP trunking may allow a compatible PBX to remain in service. We assess its condition, capacity, security, support position and expected lifespan before recommending this approach.
Are alarms and lift phones included in a phone system migration?
They must be included in the wider PSTN audit, but they may require a separate solution from the alarm, lift or equipment provider. Every device needs compatibility confirmation and end-to-end testing.
How can we check whether our business is ready?
Book a structured review covering telephone services, numbers, connected equipment, internet connectivity, power, failover, cabling and migration ownership. You can arrange a free review with Helping Hand Technology Services.
What does a business need in place after the switch-off?
Most organisations need a suitable IP voice service, dependable internet connectivity, secure network infrastructure, number-porting support and a tested continuity plan. The right combination depends on the existing phone system and the operational importance of voice communications.
Call 0330 174 9142 to arrange a free review, on site, by phone or on Teams.