BUSINESS GUIDE
ISDN Switch Off 2027: Dates, Costs and What Replaces ISDN
The ISDN switch off completes on 31 January 2027, when every ISDN2 and ISDN30 line in the UK stops working permanently. Openreach has not accepted new ISDN orders anywhere in the country since September 2023.
If your business still runs a phone system on ISDN, you need to move to VoIP or SIP trunking before that date. This guide covers the confirmed dates, what stops working, what it costs, and how the migration actually works.
Reading time: 18 minutes | Written by Kully Hothi, Sales Director, The VoIP Shop
In UK telecoms since 2011 | Last updated: September 2026
About the Author
ISDN switch off at a glance
- Final switch off date
- 31 January 2027
- What closes
- ISDN2 and ISDN30 business lines
- Stop sell began
- September 2023, nationwide
- Original deadline
- December 2025, moved in May 2024
- Replacement
- VoIP or SIP trunking
- Who is affected
- Any business with a phone system on ISDN
On this page
- What is the ISDN switch off?
- ISDN switch off date and timeline
- What is an ISDN line?
- Is ISDN still used in the UK?
- Why is ISDN being phased out?
- What stops working
- What is replacing ISDN?
- ISDN costs and VoIP costs
- ISDN readiness checker
- How to migrate to VoIP
- Broadband after ISDN
- Results for UK businesses
- ISDN switch off FAQs
What is the ISDN switch off?
The ISDN switch off is the permanent closure of the UK's ISDN telephone network. On 31 January 2027, Openreach retires the analogue and ISDN voice network entirely, and every ISDN2 and ISDN30 line stops carrying calls.
It is not a gradual decline you can wait out. Since September 2023 there has been a nationwide stop sell, which means no business anywhere in the UK can order a new ISDN line, add channels to an existing one, or change an ISDN product. Existing lines keep working until the switch off date, and then they do not.
The switch off is one part of Openreach's wider move to an all-IP network. The ISDN element matters most to businesses, because ISDN is what business phone systems have been connected to for the last thirty years.
What does ISDN stand for?
ISDN stands for Integrated Services Digital Network. It is a digital service that carries voice calls over the traditional copper telephone network, in fixed channels. Each channel carries one call, so a business with eight channels can make or receive eight simultaneous calls.
ISDN was introduced in the UK in the 1980s as an upgrade on analogue lines. It is now being retired because the copper network underneath it is being retired.
ISDN switch off date and timeline
The ISDN switch off date is 31 January 2027. This is the date Openreach has confirmed for retiring the analogue and ISDN network, and it applies across the whole of the UK.
The date has moved once. The original deadline was December 2025, and in May 2024 BT confirmed it was being pushed back to January 2027 to give more time for vulnerable customers and critical services to migrate safely.
- September 2023 Nationwide stop sell Openreach stopped accepting orders for new ISDN and PSTN lines at every UK exchange. Existing lines continue, but nothing new can be ordered and no changes can be made.
- May 2024 Final date moved to January 2027 BT confirmed the switch off was moving from December 2025 to January 2027, giving businesses an extra thirteen months.
- Now Migration phase Businesses are moving ISDN phone systems to VoIP and SIP trunking. Openreach is also working through its programme of exchange closures.
- 31 January 2027 ISDN switch off completes All ISDN2 and ISDN30 lines cease. Any phone system, alarm, lift line or terminal still connected to ISDN stops working.
Government guidance describes the upgrade as expected to be complete for most customers by January 2027, and notes that not every analogue service will be switched off by then. For businesses on ISDN, though, the position is straightforward: ISDN2 and ISDN30 are going, and there is no ISDN product to move to.
Has BT switched off ISDN yet?
Not completely. BT has stopped selling ISDN, so you cannot order a new line or add channels, but existing ISDN lines are still live until the January 2027 date. What has already gone is your ability to expand or change what you have.
In practice, many businesses find the switch off arrives earlier than 2027, because their exchange is scheduled for closure before then, or because their provider migrates them as part of a planned programme. If you have had a letter about your exchange, treat that date as your deadline rather than January 2027.
What is an ISDN line?
An ISDN line is a digital phone line that carries calls in fixed channels over copper. Unlike a single analogue line, which carries one call, an ISDN line is sold in channel bundles, which is why businesses used it for phone systems that needed several calls at once.
There are two products in the UK, and the difference matters when you plan a migration.
ISDN2 switch off and end of life
ISDN2, sometimes sold as ISDN2e, carries two channels on a single line, so two simultaneous calls. It was the standard choice for small offices, shops and sites that needed a little more capacity than a single analogue line.
ISDN2 reaches end of life on 31 January 2027, the same date as everything else on the ISDN network. If your ISDN2 line feeds a small phone system, a card terminal or a lift line, each of those needs its own replacement plan.
The grey or cream box on the wall where an ISDN2 line terminates is the network termination equipment, often called an ISDN2 box. It becomes redundant at switch off and does not need replacing, because VoIP runs over your internet connection instead.
ISDN30 switch off and end of life
ISDN30 carries between 8 and 30 channels on a single connection, so 8 to 30 simultaneous calls. It is a business-only product, and it is almost always connected to an on-premise phone system or PBX. If you have ISDN30, you have a phone system.
ISDN30 also ends on 31 January 2027. Because ISDN30 sites tend to be larger, with call routing, direct dial numbers, call queues and sometimes multiple sites on one system, ISDN30 migrations need the most planning. The number of channels is not the whole picture either, because VoIP does not work in fixed channels, so the right comparison is your busiest hour of concurrent calls, not the channel count you happen to be paying for.
Can I still install a new ISDN line?
No. Since the nationwide stop sell in September 2023, no UK provider can install a new ISDN line, add channels to an existing one, or move an ISDN service to a new address. If you are opening a site, expanding, or relocating, VoIP or SIP is the only option available.
Existing ISDN line rental continues until switch off, but you are paying for a service you cannot change and that has a fixed end date.
Is ISDN still used in the UK?
Yes, but it is closing. ISDN is still carrying calls for UK businesses today, and will until 31 January 2027. What is no longer possible is buying it, growing it or changing it.
The businesses still on ISDN tend to fall into three groups: sites with an older PBX that works perfectly well and has never needed replacing, organisations with equipment wired to a phone line that nobody has audited in years, and multi-site businesses where one or two locations were missed in an earlier upgrade.
If you are unsure whether you are still on ISDN, the quickest checks are your phone bill, which will show ISDN2 or ISDN30 as a line item, and your comms room, where an ISDN30 connection terminates in a network termination unit next to your phone system.
Why is ISDN being phased out?
ISDN depends on the copper telephone network, and that network is being retired in favour of fibre and Internet Protocol. Once the copper voice network goes, the services running on it go with it.
The practical reasons are straightforward. The copper network is decades old and increasingly expensive to maintain, with parts and expertise both harder to source. It is also being replaced by full fibre, which Openreach is rolling out across the UK, and running two national voice networks side by side is not sustainable. Voice over IP does everything ISDN does and adds features that ISDN cannot support at all, such as connecting mobile and desktop apps to the same number.
The UK is not unusual here. Telephone operators across Europe have already retired or scheduled the retirement of their ISDN networks.
What stops working when ISDN switches off?
The switch off affects more than phone calls. Anything that sends data or signals over an ISDN or analogue line needs checking, and some of it carries legal obligations.
Equipment affected by the ISDN switch off
| Equipment | What happens at switch off |
|---|---|
| ISDN2 and ISDN30 lines | Cease completely. No calls in or out. |
| On-premise PBX on ISDN trunks | Loses all inbound and outbound calling. The system may still work internally but cannot reach the outside world. |
| Intruder and fire alarms that dial out | Lose their monitoring path. Need IP or mobile signalling, and this often means new hardware. |
| Lift emergency phones | Stop working. Lift emergency communication is a legal requirement, so this cannot be left until last. |
| Card payment and EPOS terminals on a phone line | Lose their connection. Need to move to IP or mobile data. |
| Fax and franking machines | Stop working over IP in their current form. Fax to email is the standard replacement. |
| Door entry and intercom systems | Lose the ability to dial out. Need an IP-based replacement. |
| CCTV using dial-up access | Loses remote access and alerting. |
Lift emergency phones and monitored fire or intruder alarms are the two categories where failure is a compliance problem, not just an inconvenience. Both usually need a third party to attend, and both have lead times. Start those conversations before you plan the phone system itself.
What is replacing ISDN?
VoIP and SIP trunking are replacing ISDN. Both carry calls over your internet connection instead of a copper phone line, and both let you keep your existing phone numbers.
ISDN and analogue services and their replacements
| Legacy service | Modern replacement | How it connects |
|---|---|---|
| ISDN2 / ISDN30 voice | VoIP or SIP trunking | Cloud-hosted voice over your internet connection |
| On-premise PBX | Cloud phone system | Hosted in the cloud, no on-site call hardware |
| Copper-delivered broadband | FTTP full fibre or SoGEA | A data service that does not need an analogue phone line |
| Analogue fax | Fax to email | Sent and received as email attachments |
| Dial-out alarm signalling | IP or mobile signalling | Over broadband or a mobile network, often dual path |
VoIP as an ISDN replacement
VoIP replaces both the lines and the phone system. Calls run over your broadband, the system is hosted in the cloud, and users can be on a desk phone, a laptop or a mobile on the same number. For most businesses coming off ISDN this is the straightforward route, because it removes the on-premise hardware at the same time as the lines.
It also removes the channel limit. Instead of paying for a fixed number of channels whether you use them or not, capacity scales with what you need.
SIP trunking if you are keeping your phone system
If your PBX is relatively modern and you would rather keep it, SIP trunking replaces the ISDN lines feeding it while the system stays in place. Your phone system carries on working as it does now, with SIP trunks delivering the calls instead of ISDN30.
This is usually the cheaper migration in the short term and the right answer when a phone system has years of life left. It is worth checking whether your PBX is SIP-capable first, as older systems may need a card or a licence.
ISDN costs and what VoIP costs instead
ISDN has become an expensive way to carry a call, and deliberately so. Wholesale pricing on legacy copper products has been rising ahead of the 31 January 2027 switch off, while the cost of internet connectivity has fallen. In the UK market ISDN channels currently sit at roughly £25 to £50 per channel, per month.
How much does an ISDN line cost?
It depends on which product you are on and how many channels you are contracted for. Because both ISDN products are sold in fixed blocks, the monthly cost adds up faster than the per-channel figure suggests.
Typical UK ISDN costs, September 2026
| Product | Typical monthly cost | Why |
|---|---|---|
| ISDN2e
Small offices |
£38 to £101+ per month | Sold with a minimum of two channels, so line rental accumulates even on a small site. The range depends on your retail provider. |
| ISDN30e
Larger sites |
£25 to £45 per channel £200 to £360 minimum |
A minimum of 8 channels must be active, so an entry-level ISDN30 circuit starts at that baseline before any call charges. |
| Ancillary charges | Uplifts applied | DDI ranges and alternative routing have seen price uplifts across business communications resellers. |
Figures are indicative UK market rates as at September 2026 and vary by provider and contract. Your own bill is the accurate number.
Why ISDN prices have risen
Three things are pushing legacy line costs up at the same time:
- Wholesale price increases on copper. Openreach has applied a series of increases to wholesale line rental on legacy products ahead of the switch off, with a further increase scheduled for October 2026. The effect is that maintaining a copper-based service now costs materially more than it did in early 2025, while IP connectivity has become cheaper.
- Stop sell leaves you where you are. Since September 2023 no new ISDN lines can be bought, and existing lines cannot be expanded, modified or moved like-for-like between suppliers. You are held at your current capacity, at whatever your existing carrier charges.
- Hardware scarcity. The PBX cards and on-premise hardware that service ISDN lines are no longer mass-produced. Repairs are expensive when parts can be found at all, and if the hardware fails you can be left without service.
ISDN and VoIP compared
Legacy ISDN against hosted VoIP
| Cost factor | Legacy ISDN setup | Hosted VoIP |
|---|---|---|
| Monthly cost | £25 to £50 per channel | From £13.95 per user |
| Upfront hardware | On-premise PBX, a significant capital cost | Minimal to none. Cloud-hosted, with apps or IP desk phones |
| Scalability | Fixed blocks. Pairs on ISDN2, minimum 8 channels on ISDN30 | Per user, changed on demand |
| Maintenance | Separate support contract | Support and maintenance included in the monthly price |
| Installation fee | Varies | None |
The comparison that matters is not per channel against per user, it is your whole monthly bill against the same capacity on VoIP. An ISDN30 site paying for 16 channels because it needs 11 concurrent calls is paying for five it never uses. VoIP is priced per person, so that waste disappears.
What VoIP costs
Our hosted VoIP plans are published, per user per month, with no installation fee:
Standard Voice
Premium AI
Ultimate AI + CRM
Prices verified 31 August 2026. See plans and pricing for what is included in each.
Where the savings come from
Three places, in roughly this order of size. You stop paying ISDN line rental and channel charges altogether, which is usually the largest single line item. Call rates are lower, and internal calls between users and sites are free regardless of location. And you stop paying to maintain, repair and eventually replace on-premise phone system hardware.
There is a fourth saving that does not appear on a phone bill: you stop paying for capacity you do not use. ISDN30 is sold in channel blocks, so a site that needs eleven concurrent calls buys sixteen channels. VoIP is priced per user.
ISDN switch off readiness checker
Tick everything your business still has. You will get a risk level and a prioritised action list based on your own answers.
How to migrate from ISDN to VoIP
A migration off ISDN follows the same six stages whether you have one ISDN2 line or a multi-site ISDN30 estate. The difference is how long each stage takes.
Watch: moving from analogue and ISDN lines to cloud VoIP
A short walkthrough of what the switch off means for a business still on old lines, what needs auditing before you migrate, and how a cloud phone system replaces both the lines and the phone system.
Is Your Business Ready for the UK Big Switch Off? — The VoIP Shop on YouTube
Step 1: Free ISDN system assessment
We look at what you actually have: your ISDN lines and channels, your phone system, your numbers, and every device connected to a phone line. This is where the alarms, lift lines and card terminals get found, and it is the stage most often skipped.
Step 2: Requirements planning for your ISDN replacement
We work out what you need rather than what you currently pay for. That means concurrent calls at your busiest hour, how many people need a handset against an app, which numbers must be kept, and what your call routing needs to do.
Step 3: Tailored VoIP solution design
The design covers the platform, handsets, call routing, and whether SIP trunking to your existing PBX is a better fit than replacing the system. If your broadband will not support the call volume, this is where that is identified.
Step 4: Implementation proposal and costs
A written proposal with the monthly cost, any hardware cost, the migration plan and the timeline. No installation fee, and the comparison against what you pay for ISDN today is set out in full.
Step 5: ISDN to VoIP migration planning and number porting
Numbers are ported from ISDN to the new platform, which is the part that needs the most lead time. Handsets are configured before they arrive on site, and the cutover is scheduled so there is no gap in service. Porting timescales vary by number range and losing provider, so we confirm dates in writing before the cutover is booked.
Step 6: Go live and ongoing support
The system goes live, staff get training, and the old ISDN lines are ceased once everything is confirmed working. Support is available 24/7, with business operating hours of 9:00am to 5:30pm, Monday to Friday.
A single-site ISDN2 migration is usually straightforward. A multi-site ISDN30 estate with alarms, lifts and card terminals takes longer, and the constraint is rarely the phone system. It is the third parties who need to attend site for the alarm and lift work. Plan backwards from those.
Broadband after ISDN: FTTP and SoGEA
There is a lot of confusion here, so it is worth being precise. The 31 January 2027 date applies to the analogue and ISDN voice network. Openreach's own wording is that the analogue network will be retired by that date. It is not a broadband switch off.
FTTP full fibre is not affected by the ISDN switch off. It does not use the analogue voice network and nothing changes for it on 31 January 2027.
Copper-delivered broadband is a separate matter. ADSL and older FTTC connections run over copper, and copper is being retired through Openreach's exchange closure and copper retirement programme. That programme runs on its own timetable, not on the 2027 voice deadline, and it is why some businesses are contacted about their broadband well before or after the ISDN date.
Two replacements matter for businesses coming off ISDN:
- FTTP — full fibre to the premises. The fastest and most resilient option, and the right one where it is available.
- SoGEA — Single Order Generic Ethernet Access. A broadband service delivered without an underlying analogue phone line, which is what makes it the natural fit alongside VoIP. It is the sensible option where FTTP has not reached you yet.
If your VoIP calls will run over the same connection as everything else, the assessment in step 1 should confirm the connection can carry the call volume before anything is ordered.
Results for UK businesses leaving ISDN and legacy phone lines
Three recent migrations off ageing lines and on to cloud phone systems, with what changed for each business.
ISDN lines replaced
Peter Dunn Solicitors, 2 sites
A law firm running a legacy PBX on 8 ISDN lines at head office and 4 at a satellite office. Spare parts were becoming hard to source and there were no remote working apps. Both sites now run one Yeastar cloud system with call recording, AI transcription, inter-site transfer and a direct dial number for every solicitor.
hours a year saved
Mountbatten School, Hampshire
A 1,458-pupil secondary school with 170 staff moved off legacy lines to a Yeastar cloud system with a 1Gbps leased line and FTTP failover, plus an AI absence line integrated with the school MIS. Ten times the bandwidth, and zero downtime during migration.
Read the case studytelephony costs cut
Dental Tech, 5 sites
Four clinics and a laboratory unified on one fully managed Yeastar system with multi-site routing, call recording and live wallboards. Next-working-day porting and no downtime.
Read the case studyAll certifications current as at September 2026.
ISDN switch off FAQs
When is the ISDN switch off date?
The ISDN switch off date is 31 January 2027. On that date all ISDN2 and ISDN30 lines in the UK cease. The original deadline was December 2025, and BT confirmed the move to January 2027 in May 2024.
Has BT already switched off ISDN?
Not yet. BT stopped selling ISDN in September 2023, so no new lines or channels can be ordered anywhere in the UK, but existing lines still work until 31 January 2027. Some businesses will be migrated earlier if their exchange is scheduled to close before that date.
When is ISDN2 end of life?
ISDN2 reaches end of life on 31 January 2027, the same date as the rest of the ISDN network. New ISDN2 lines have not been available to order since September 2023.
When is ISDN30 end of life?
ISDN30 reaches end of life on 31 January 2027. Because ISDN30 usually feeds an on-premise phone system with call routing and direct dial numbers, ISDN30 migrations need more planning time than ISDN2.
What is ISDN30 and how many channels does it have?
ISDN30 is a business ISDN product carrying between 8 and 30 channels on one connection, so 8 to 30 simultaneous calls. It is used almost exclusively with an on-premise PBX. ISDN2 by comparison carries two channels.
How much does an ISDN line cost?
ISDN2e typically costs between 38 and 101 pounds or more per month, because it is sold with a minimum of two channels. ISDN30e runs at roughly 25 to 45 pounds per channel, and because a minimum of eight channels must be active, an entry-level ISDN30 circuit starts at around 200 to 360 pounds per month before call charges. Hosted VoIP starts from 13.95 pounds per user per month with no installation fee. Figures are indicative UK market rates as at September 2026 and vary by provider and contract.
Why has ISDN become so expensive?
Three things at once. Openreach has applied a series of increases to wholesale line rental on legacy copper products ahead of the switch off, with a further increase scheduled for October 2026. Stop sell means you cannot expand, modify or move an ISDN service between suppliers, so you are held at your current capacity and price. And the PBX cards and hardware that service ISDN lines are no longer mass-produced, which makes repairs expensive when parts can be found at all.
Can I still order a new ISDN line?
No. The nationwide stop sell in September 2023 ended all new ISDN orders. You cannot install a new ISDN line, add channels to an existing one, or move an ISDN service to a new address. VoIP or SIP trunking are the available options.
Can I keep using ISDN after 2027?
No. Once the network is switched off there is no ISDN service to use. There is no paid extension and no legacy option, because the network itself is being retired rather than the product being withdrawn.
What happens if I do not upgrade before the switch off?
Your phone lines stop carrying calls. Alongside that, anything else connected to those lines stops working, which typically means alarm monitoring, lift emergency phones, card terminals and fax. For most businesses the phone system going down is the visible problem and the alarm or lift line is the serious one.
Will I lose my business phone numbers?
No. Existing geographic numbers can be ported from ISDN to a VoIP platform, including direct dial ranges. Your provider manages the process. Porting needs to be scheduled in advance, so it is the part of a migration that should be started early.
How long does ISDN to VoIP migration take?
It depends on size and on what else is connected to your lines. A single-site ISDN2 migration is quick. A multi-site ISDN30 estate with alarms, lifts and card terminals takes longer, and the limiting factor is usually the third parties who have to attend site rather than the phone system itself.
Will VoIP work during a power cut?
VoIP needs power and an internet connection, so a power cut affects it in a way an old analogue line did not. In practice most businesses handle this by diverting calls to mobiles automatically when the connection drops, which is configured as part of the setup. Sites that need guaranteed voice during an outage can add battery backup for the router and handsets.
Can I migrate gradually or must it be all at once?
Gradually is often the better approach for larger estates. Sites or departments can move in phases, with the old and new systems running alongside each other and calls routed between them during the transition. What cannot be phased indefinitely is the deadline, so a phased plan still needs to complete before 31 January 2027.
Does the ISDN switch off affect my broadband?
Not directly. The 31 January 2027 date applies to the analogue and ISDN voice network, not to broadband. FTTP full fibre is not affected at all. ADSL and older FTTC connections run over copper, and copper is being retired through a separate Openreach programme with its own timetable, which is why broadband changes may reach you at a different time to the voice switch off.
Still on ISDN? Let's plan your migration
We will audit your lines, your phone system and every device connected to a phone line, then give you a written plan and a fixed monthly cost. No installation fee.
Written By | About the Author
Kully Hothi
Sales Director
Kully Hothi is Sales Director at The VoIP Shop and one of the company's lead authors. He has worked in UK telecoms since 2011, and has taken thousands of businesses through the move off ISDN and analogue lines onto cloud phone systems, porting numbers and cutting over without downtime. He is sales certified across 3CX, Yeastar and Cisco as well as Openreach and all four major UK mobile networks, which is why he looks at phones, mobiles and connectivity together rather than as three separate problems. More about Kully Hothi.
