PSTN Switch-Off for Small Businesses: What to Do

A small business still using a PSTN, ISDN or ADSL service must move it to a suitable digital replacement before 31 January 2027. Start with an inventory of every line and every device attached to it, not just desk phones. Card terminals, monitored alarms, lift phones, door entry, CCTV diallers, fax machines and telemetry may use an analogue line without appearing on the phone bill by a recognisable name.

The UK Government says all users of the Openreach PSTN must be migrated by 31 January 2027. Openreach supplies the underlying access network, but your communications provider sells and migrates your service. Equipment suppliers must separately confirm whether each connected device works over the proposed replacement. A promise that the new phone system works does not prove that an alarm or payment terminal will work.

PSTN switch-off business checklist

1. Find every line: match phone bills, socket labels, alarm contracts and equipment records to each business site.
2. Name what uses it: record the number, device, supplier, business owner and what happens if it fails.
3. Ask the device supplier: obtain written compatibility advice for the exact make, model and monitoring service.
4. Choose the replacement: hosted VoIP, SIP, a digital provider service, mobile connectivity or another approved solution.
5. Plan resilience: decide how calls and critical devices work during power, broadband and mobile outages.
6. Test before closure: run old and new services in parallel where risk justifies it, then record every successful test.

Which small-business services are affected?

The switch-off affects more than voice calls. BT Business lists alarms, EPOS machines, door-entry systems, CCTV and fax among products that may use traditional lines. GOV.UK guidance also identifies tills, vending machines, franking machines and printers. Treat those examples as prompts for an audit, not proof that a particular device is affected.

What replaces PSTN and ISDN?

Most small firms will replace voice calls with VoIP, but the right form depends on the existing phone system. Hosted VoIP puts the call platform in the provider's cloud and can serve desk phones, mobiles and computer apps. SIP trunking carries internet-based calls to a compatible on-site PBX. A simple digital voice line from a broadband provider may suit a single number with few call-handling needs.

SIP trunking is not a direct continuation of PSTN. It connects a compatible business phone system over IP. Keeping an old PBX can reduce handset changes, but only if its maintainer supports the proposed SIP service. Hosted VoIP removes more on-site telephony equipment and can make remote working easier, but it creates a clear dependency on local power, connectivity and the provider's platform.

Do not buy a voice replacement for a non-voice device until its supplier has approved the design. An analogue terminal connected through an adapter may appear to dial but still fail to transmit data reliably. The safer option may be an Ethernet model, a managed mobile communicator or a replacement designed for IP networks.

ISDN switch-off: what changes for a phone system?

ISDN2 and ISDN30 services are included in the retirement of the old Wholesale Line Rental network. A business using multiple channels, a switchboard or Direct Dial In numbers should document every number and call route before migration. Confirm which numbers will be ported, which can be retired, how long the port should take and who can divert calls if the planned change fails.

BT Business says ISDN, Featureline, multiline and some broadband access products cannot be moved automatically under its protective migration programme. Do not cancel the existing service before the new provider confirms the number port. Cancellation can jeopardise a number and removes the safest route to a parallel test.

Power cuts, broadband failure and business continuity

A digital phone or device path can fail when mains power or broadband fails, even where the old analogue line worked without local power. Trace the whole path: handset or device, adapter, switch, router, firewall and fibre terminal. A battery on an alarm panel is not enough if the router it needs has no backup.

Ofcom says providers must offer at least one solution enabling a landline-dependent customer to contact emergency organisations for at least one hour during a power cut. It recognises that a sole trader or small office with no mobile signal may need that protection. This safeguard is not a general uptime guarantee for a PBX, card machine or alarm.

Set a recovery objective for each service. A shop may accept a mobile card-terminal fallback for an hour, while a monitored fire alarm or lift phone needs a supplier-approved design and testing regime. Consider two genuinely independent routes where an outage stops trading or creates a safety risk. Two services sharing the same router, power socket or access circuit are not independent.

A safe migration and test plan

For a critical service, prove the replacement before the cease order. The useful international model is a device-led readiness check: Australia's NBN guidance asks businesses to identify PBX systems, EFTPOS, alarms, lift phones and other equipment, then contact the relevant equipment provider. For a UK small business, add a named owner, written supplier approval and a witnessed end-to-end test.

1. Export the current numbers, extensions, call routes and supplier contacts.
2. Install the new connection and retain the old service in parallel where the supplier permits it.
3. Test incoming and outgoing calls, caller ID, voicemail, transfers, hunt groups and emergency-call location handling where applicable.
4. Ask each device owner to run an end-to-end test with the receiving party, such as the alarm monitoring centre or acquiring bank.
5. Test the agreed outage fallback under supplier instructions.
6. Only then approve the port or closure. Record the asset, result, date and person who accepted it.

What a small business should do before 2027

Contact your communications provider now if any line remains unidentified or no migration date is booked. Ask for the product name on each circuit, whether it depends on PSTN, ISDN, WLR or ADSL, and the proposed replacement. Then verify connected equipment with its own supplier. Openreach advises customers to act before the deadline because late migration can leave too little time to find compatibility problems.

For connectivity and resilience choices, compare UK business broadband providers and read our guide to static IP business broadband. Our small office broadband setup guide covers the wider router, backup and service-level checklist that a VoIP migration should sit alongside. For the domestic change, including ordinary home phones and telecare, use the UK landline switch-off guide. The business task is broader because the same unnoticed line can support calls, safety equipment and payment systems.