When is the UK PSTN switch-off?

31 January 2027. BT Openreach is switching off the PSTN and ISDN lines permanently on that date. No extensions are planned. New PSTN line sales stopped in September 2023; existing lines are being migrated through 2024-2027.

What does a UK business need to replace before 2027?

Traditional office landlines, alarm monitoring circuits, lift emergency phones, PSTN-based payment terminals, and any dial-up modem services (BMS, CCTV callbacks, remote monitoring). Replace with VoIP, GSM (mobile-based), or IP-based alternatives.

What about alarms and lift phones — will they stop working?

Yes if they use PSTN. Intruder alarms, fire alarms, and lift emergency phones often use PSTN lines. They need migration to IP or GSM-based signalling (BT Redcare IP, CSL DualCom, GSM dialler units). Check with your alarm and lift providers — this is often overlooked.

PSTN Switch-Off January 2027: Business Mobile & VoIP Readiness Guide (2026)

Last updated: April 2026

BT Openreach is switching off the UK's Public Switched Telephone Network (PSTN) permanently in January 2027. Every traditional copper phone line in the country will stop working. If your business has any PSTN lines — office landlines, alarm circuits, lift phones, payment terminals — you need a migration plan before the end of 2026.

This guide covers what's actually changing, how mobile and VoIP fit, and a practical checklist.

What's being switched off

The entire Public Switched Telephone Network, plus ISDN lines and some other legacy circuits. Openreach already stopped selling new PSTN and ISDN lines in September 2023. Existing lines are being migrated to digital (VoIP) equivalents through 2024-2027.

Deadline: 31 January 2027 — hard switch-off. No extensions. No exemptions for "we haven't got round to it yet."

What you actually need to replace

Traditional office landline

Most obvious. Replace with cloud VoIP — phone numbers ported, system handles call routing, desk phones or softphone apps replace copper handsets.

Many small UK businesses will skip formal VoIP and go mobile-first — just the mobile number on business cards and voicemail. For solo operations and freelancers, this often works. For larger teams, proper VoIP makes sense.

Alarm circuits

Intruder alarms and fire alarms often use PSTN lines to signal Alarm Receiving Centres (ARCs). Need migration to IP-based signalling (BT Redcare IP, CSL DualCom IP equivalents). This is often overlooked and causes serious issues. Check with your alarm provider.

Lift phones

Lift emergency phones are legally required (BS EN 81-28). Most use PSTN. Need migration to GSM (mobile-based), VoIP, or cellular backup systems.

Payment terminals

Older card machines using PSTN will stop. Most are now IP-based or GSM-based already, but verify with your card provider.

Fax machines

If you still have one (some industries, particularly legal and medical, do): PSTN fax stops. Options: eFax service, scan-to-email, or replace the workflow entirely.

Monitored services

Building management systems, boiler-monitoring, CCTV voice callbacks, call-outs from remote plant — anything using a dial-up modem over PSTN needs replacing.

Where mobile fits

For many UK SMBs, the cleanest PSTN-switch-off answer is mobile-first with VoIP backup:

Primary business number moves to cloud VoIP or a Teams Phone extension — rings mobile app plus desk softphone
Staff use business mobile SIMs as their primary phone — VoIP app on the mobile for office number; SIM for personal mobile number
Alarm and lift circuits migrate to dedicated IP or GSM-based solutions (separate product)

This setup means:

Customers calling the business number reach you anywhere (mobile app + softphone)
Staff can WFH or travel without losing calls
No copper lines to maintain
Inclusive EU roaming means phones work abroad (if you travel)

The mobile-first approach for small businesses

For UK sole traders and micro-businesses (1-5 people), the simplest answer often is: skip VoIP entirely, go mobile-only with a dedicated business mobile number.

Print the business mobile number on cards, van, website
Use a good voicemail setup
Switch off outside hours if you want (you own the switch)
Optional: add a basic VoIP number (~£5/month for a UK landline-style number that rings your mobile)

Works surprisingly well for many. Doesn't work if you need auto-attendants, multiple extensions, or call recording.

Practical checklist

Now (April-August 2026)

Audit every phone line in your business — office, warehouse, alarm, lift, fax, payment terminals
List every number you receive calls on
Get quotes for VoIP replacement or mobile-first migration
Check alarm provider about alarm line migration
Check lift provider about lift phone migration

Autumn 2026

Begin migration — early movers avoid the end-of-year rush
Port numbers to VoIP or decide to release legacy numbers
Deploy business mobile SIMs if switching to mobile-primary
Install any new VoIP hardware (desk phones, headsets)

December 2026

Complete all migrations
Test alarms, lifts, payment terminals with new circuits
Brief staff on new setup

After 31 January 2027

Confirm all services operational
Cancel any redundant legacy line accounts

What waiting until 2027 costs

Two specific risks:

1. Installation backlog

Every UK SMB leaving it to the last quarter hits a massive backlog. Installers booked out, number porting queues, alarm monitoring upgrades delayed. You might be without service for days.

2. Emergency replacement costs

If your alarm stops working on 1 February 2027 because no one migrated the circuit, emergency replacement costs 2-3x normal pricing. Same for lift phones (which are legally required).

What CTN can do

For UK businesses preparing for the PSTN switch-off:

Business mobile deployment — SIMs and handsets for mobile-primary migration
VoIP setup — cloud phone systems via CTN partner platforms; call routing, auto-attendants, softphones
Number porting — move existing business numbers to VoIP or keep them ringing to mobile
Bundle pricing — mobile + VoIP + Microsoft 365 together saves 10% on Microsoft

Not in scope for us: alarm panel migration, lift phone installation — these are specialist installers. But we can point you at reputable providers if asked.

FAQs

Is the PSTN switch-off definitely happening in January 2027?

Yes. BT/Openreach confirmed the timeline; OFCOM has signed off. No realistic chance of delay. Last 30 years, public switched telephony has steadily declined — less than 10% of UK phone calls still use it by volume.

What about businesses that never needed a phone line?

Many SMBs already operate mobile-only — tradespeople, consultants, creative freelancers, small e-commerce. They're not affected directly. But they should check alarm and monitored-service connections in case any still use PSTN.

Can I keep my existing landline number?

Yes — number porting to VoIP or mobile forwarding preserves the number. The change is the infrastructure behind it, not the number you've been advertising for 20 years.

How much does VoIP cost versus a PSTN landline?

VoIP is usually cheaper at comparable spec. A basic UK VoIP line is £5-10/user/month (vs £20-30 for old PSTN with call plans). A full cloud phone system (auto-attendant, recording, mobile app) is £15-25/user/month.

Do I need desk phones or can I go fully mobile / softphone?

Depends on your setup. Reception and front-desk usually still benefits from a desk phone (appearance, longer calls). Sales and mobile staff often work fine on softphones (Teams, proper VoIP apps). Many businesses mix.

What about fax? My accountants/solicitors still use it.

eFax services let you send and receive faxes by email — no physical machine needed. Most UK accountants and solicitors have moved to secure email anyway. Check what your contacts actually use today.

Getting a quote

Call 01743 598025 or request a quote. PSTN switch-off and mobile/VoIP migration is our bread and butter. Free audit of your current landlines and mobile setup, honest quote with migration plan.