If your business still uses a traditional landline or ISDN system, you have less than two years to act. Openreach is switching off the UK’s entire Public Switched Telephone Network (PSTN) in January 2027 — and when it goes, your phones go with it. This guide explains exactly what the switch-off means, who it affects, and the steps you need to take right now.
The short answer:
- The UK PSTN and ISDN networks are being permanently switched off in January 2027
- Any business using a traditional copper phone line, ISDN, or ADSL broadband will be affected
- New ISDN connections have been unavailable since September 2023 — the clock is already running
- You need to switch to a VoIP or IP-based phone system before the deadline
- The migration is straightforward — most businesses are fully up and running within 10 working days
What is the PSTN switch-off?
The PSTN — Public Switched Telephone Network — is the original copper wire telephone network that has connected UK homes and businesses since the 1800s. Openreach, which owns and maintains most of the UK’s telephone infrastructure, is shutting it down entirely by January 2027.
That means every traditional phone line, every ISDN connection, and every ADSL broadband service that depends on the copper network will stop working on that date. Not “gradually phased out.” Off. Permanently.
The switch-off follows a clear timeline:
- September 2023: Openreach stopped accepting new ISDN orders across the UK
- January 2027: The full PSTN and ISDN switch-off. All copper-based phone lines cease to function
If you have not moved to an IP-based system by January 2027, you will lose your phone service with no fallback.
Who does the PSTN switch-off affect?
The honest answer is: most UK businesses to some degree. You are affected if your business uses any of the following:
Traditional phone lines (POTS/PSTN lines)
Standard analogue landlines — the kind that came with your office — run on the copper PSTN. These will stop working entirely.
ISDN2 or ISDN30 lines
ISDN (Integrated Services Digital Network) is the business-grade version of the copper network. It is widely used for multi-line phone systems, CCTV, alarm monitoring, and card payment terminals. All ISDN services are being withdrawn.
ADSL or ADSL2+ broadband
ADSL broadband runs over the copper phone network. If your internet connection is ADSL, it will go offline with the PSTN. You will need to upgrade to FTTC, FTTP (full fibre), or a leased line before the deadline.
Fax machines, PDQ terminals, and alarm systems
Many businesses overlook these. Fax machines, some card payment terminals, door entry systems, and monitored alarms connect via PSTN lines. All of them need checking.
What happens if you do nothing?
Your phone lines stop working on the switch-off date. There is no extension, no grandfathering of existing services, and no grace period from Openreach. If you have not migrated, you are unreachable by phone.
For most businesses, that means:
- Customers cannot call you
- You cannot call suppliers, banks, or partners
- Any system relying on a PSTN connection (alarms, CCTV, card terminals) fails
- Number continuity is lost if you have not ported your existing numbers in advance
The earlier you migrate, the more control you have over the process. Businesses that leave it until late 2026 risk being caught in a backlog of last-minute migrations.
What should you switch to?
The successor to PSTN and ISDN is VoIP — Voice over Internet Protocol. VoIP routes calls over your internet connection instead of the copper network. It is more reliable, cheaper to run, and packed with features that traditional lines simply cannot offer.
There are two main routes:
Hosted VoIP (cloud phone system)
Your phone system is managed in the cloud by your provider. Calls run over your existing broadband or leased line. No on-site hardware beyond handsets or a headset. This is the right choice for most SMEs.
You keep your existing on-site phone system (PBX) but replace the PSTN connection with a SIP trunk. Best for businesses with a significant investment in existing hardware they want to retain.
Both routes let you keep your existing phone numbers through number porting.
What you need to do — step by step
Step 1: Audit your current lines
Get a list of every phone number, ISDN circuit, and broadband line connected to your business. Include alarm systems, door access panels, PDQ terminals, and any other device that connects via a phone socket. Your provider’s bill is the easiest starting point.
Step 2: Check your internet connection
If you have ADSL broadband, you need to upgrade before migration. FTTC (fibre to the cabinet) or FTTP (full fibre to the premises) are the minimum requirements for reliable VoIP. If your business needs guaranteed uptime — a solicitors’ office, a GP surgery, a busy call centre — consider a dedicated leased line.
Step 3: Choose a VoIP provider
Not all VoIP providers are equal. Look for:
- A direct provider (not a reseller) with control over their own network
- Transparent pricing — monthly cost per user, no hidden line rental
- A flexible contract — you should not need to sign 24 months to switch before a forced deadline
- A free trial so you can test call quality on your connection before committing
- Local UK support you can actually reach when something goes wrong
Step 4: Port your numbers
You can take your existing business numbers with you to any VoIP provider. Number porting typically takes 5–10 working days. Do not cancel your existing lines before porting is complete — you will lose the numbers.
Step 5: Migrate and test
A competent VoIP provider handles the migration for you. You should expect to be fully operational within 10 working days — the main variable is number porting, which takes 5–10 working days and runs in the background. Test every number, every device, and every call flow before signing off.
How much does switching to VoIP cost?
Less than you are paying now, in almost every case.
Traditional ISDN lines typically cost £30–£50 per channel per month, plus call charges. A comparable VoIP setup with the same number of simultaneous calls costs a fraction of that — and includes features like voicemail-to-email, call recording, mobile integration, and ring groups as standard.
The real question is not what switching costs. It is what staying on an obsolete system costs you every month until the deadline forces you to move anyway.
How VoIPNinjas compares
VoIPNinjas is a direct UK provider — not a reseller — based in Christchurch on the South Coast. We own our infrastructure, which means better call quality, faster support, and no middleman adding margin between you and your service.
Our plans start at £5.99 per user per month (Ronin) on a 28-day rolling agreement, rising to £24.99 for Shogun — our flagship plan with unlimited minutes and calls to 55 countries. There is no long-term contract, no setup fee, and no obligation — just a free 14-day trial that you can start without giving us your card details.
Here is what PSTN migration looks like with us:
- Free consultation to audit your current lines and broadband
- Number porting handled by our team — you keep your existing numbers
- Most businesses are fully live within 10 working days of starting their migration
- Local UK support from our Christchurch team, not a call centre
We are already helping businesses across Dorset, Hampshire, and the Channel Islands make the move ahead of the 2027 deadline. The earlier you start, the smoother the switch.
Talk to our team about your PSTN migration
No tie-in, no setup fees. Most PSTN migrations are complete within 10 working days.
Get a Free Quote — or call us: 0330 043 2388
Frequently asked questions
When exactly is the PSTN switch-off?
Openreach has confirmed January 2027 as the date for the full switch-off of the Public Switched Telephone Network and all ISDN services across the UK. Some areas may experience earlier local switch-offs as Openreach completes its full-fibre rollout.
Can I keep my existing phone numbers when I switch to VoIP?
Yes. Number porting allows you to move your existing landline numbers to a new VoIP provider. The process takes between 5 and 10 working days. Your VoIP provider manages the porting request — you do not need to contact your old provider first.
Will the switch-off affect my broadband as well as my phones?
If your broadband is ADSL or ADSL2+, yes. ADSL runs over the copper PSTN and will go offline with the network. You need to upgrade to FTTC, FTTP, or a leased line before the PSTN switch-off date.
Do I need new hardware to switch to VoIP?
Not necessarily. Many VoIP systems work with analogue telephone adaptors (ATAs) that let you use existing desk phones. Alternatively, you can use IP handsets, softphones on a laptop, or a mobile app. Your provider will advise which option suits your setup.
What happens to my alarm system and PDQ terminals?
PSTN-connected alarms, CCTV monitoring, and card payment terminals will stop working at switch-off. Contact your alarm company and card payment provider now — both will need to either migrate to IP-based connectivity or switch to mobile (4G/5G) backup connections.
Is VoIP reliable enough for a business phone system?
Modern hosted VoIP on a stable broadband or leased line connection equals or exceeds the reliability of traditional ISDN. Most business-grade VoIP systems carry SLAs for uptime. Call quality is better than ISDN when your internet connection is adequate — the key variable is your broadband, not the VoIP technology.
How long does it take to set up VoIP?
With VoIPNinjas, most PSTN migrations are fully complete within 10 working days. The main variable is number porting, which takes 5–10 working days — we manage the entire process on your behalf so your existing lines stay active until the switch is done.