Quick answer
For most small UK businesses the PSTN switch-off cost is a modest one-off spend and a lower monthly bill afterwards. The phones themselves are rarely the expensive part - copper line rental disappears and UK calls are usually inclusive, so the ongoing figure typically drops. The one-off money goes on specialist items: alarm signalling, a lift emergency unit, occasionally new handsets, and any connectivity upgrade you needed anyway. Businesses that end up genuinely out of pocket are the ones with safety-critical kit they had not counted, or the ones who leave it late enough to pay emergency rates.
I look at this from the finance side, and the thing that surprises people is that the switch-off is not really a cost event - it is a repricing event. You stop renting copper and start buying a service. For most businesses that maths lands in their favour. What it does create is an unavoidable capital moment on a fixed date, which is a very different thing to budget for. This guide sets out where the money actually goes, with worked examples you can hold a real quote against. If you want an actual figure rather than a range, get a no-obligation quote and we will price your specific line inventory.
The two budgets, and why they move in opposite directions
Almost every confused conversation I have about switch-off cost comes from mixing these up:
The one-off budget is the project: replacing signalling on an alarm, fitting a GSM unit in a lift, possibly new handsets, possibly a connectivity install, plus a bit of professional time. It is real, it is finite, and it lands once.
The ongoing budget is the monthly bill afterwards. This is the part that usually improves, because you stop paying for a physical copper line per phone and start paying per user for a service with calls included.
So the honest framing is: you spend some money once to stop spending more money every month on a network that is closing. Whether that is a good deal depends entirely on how many lines you are currently renting - which is why the audit comes first.
Where the one-off money actually goes
| Item | Typical guide range (illustrative, August 2026) | Who does it | Notes |
|---|---|---|---|
| Line and bill audit | Usually free from a decent provider | You or your provider | The highest-return hour in the whole project |
| Alarm signalling replacement | Low hundreds of pounds per panel, plus any monitoring re-registration | Your alarm company | Cost varies hugely by panel age and grade |
| Lift emergency line unit | Typically the largest single line item; specialist GSM unit plus commissioning | Your lift maintenance company | Safety-critical, must work in a power cut |
| Card terminal replacement | Often free on a merchant-services refresh | Your card provider | Modern terminals already use broadband or mobile data |
| Handsets | Nil to moderate | Provider | Many existing IP handsets can be reused; analogue phones can run on an adapter |
| Connectivity install | Nil to moderate for FTTP/SoGEA; substantial for a leased line | Openreach or altnet | Often an upgrade you wanted anyway |
| Number porting | Usually included, sometimes a small per-number fee | Gaining provider | Ask whether DDI ranges are charged per number or per block |
| Phone system setup and training | Nil to moderate; frequently bundled into the term | Provider | Negotiable, especially at renewal |
Two things stand out from that table. First, the phone parts are the cheap parts. Second, the items with real money attached are the ones owned by third parties you already pay - your alarm company, your lift company, your card provider. That is why the first action in our switch-off deadline guide is to phone them, not us.
What the monthly bill looks like before and after
Here is the shape of the change, using guide ranges rather than invented precision. A traditional analogue business line has typically sat somewhere in the region of £15-£25 per line per month before the 2026 increases, with calls charged per minute on top unless you bought a bundle. Legacy wholesale line rental has risen in stages through 2026 - roughly doubling across the year - and providers pass that on, so the "before" figure is higher now than it was in January.
The "after" figure is priced per user rather than per line, usually with inclusive UK landline and mobile calls, and with features that used to be chargeable extras included as standard.
The structural saving is this: you stop paying for idle capacity. A copper line cost the same whether it carried a thousand calls or none, which is why nearly every audit we run finds lines nobody can account for. Our business phone line cost guide breaks the components down further.
Worked example: a four-line small business
An illustrative office with four analogue lines, one alarm panel and a card terminal.
| Before (legacy, mid-2026) | After migration | |
|---|---|---|
| Copper line rental | 4 lines, rising through 2026 | £0 - no copper lines |
| Call charges | Per minute, variable | Typically inclusive UK calls |
| Voice service | - | Per user, per month |
| Broadband | Separate, on top of a phone line | SoGEA or FTTP, standing alone |
| One-off spend | - | Alarm signalling; card terminal usually free; handsets often reusable |
In cases like this the ongoing bill normally comes down, and the one-off spend is dominated by the alarm. The audit frequently pays for the whole project on its own - four lines on the bill often turns out to be two lines in use, a fax line nobody has used since 2019, and a line feeding a card machine that has been on mobile data for three years.
Worked example: a business on ISDN30
An ISDN30 site is where the ongoing savings get genuinely large. You are renting a block of channels - typically anywhere from 8 to 30 - at legacy prices that have been rising all year, whether or not you use them at peak. Replacing that with SIP capacity into your existing phone system, or with a hosted system, usually cuts the per-channel cost substantially and lets you size to actual concurrency rather than the block you were sold.
The offsetting one-off is that ISDN sites are bigger projects: more numbers and DDI ranges to port, call flows to rebuild, and often a decision about whether the on-site system stays. That decision is the biggest single lever on the budget, and we cover it in can you keep your existing phone system. If your PBX is sound, keeping it is usually the cheapest compliant route by a wide margin.
For sites with several locations, sequencing matters more than unit price - see migrating multi-site and multi-line businesses.
What makes it cost more than it should
Four things, in order of how much money they waste:
- Leaving it late. Alarm and lift engineers are already booking weeks ahead. Emergency scheduling costs more than planned work, and there is no version of this where the deadline moves.
- Being migrated rather than migrating. If you do nothing, your provider will move you to their default product at their price on a fresh term. That is a commercial outcome chosen entirely by them.
- Not auditing first. Paying to migrate lines you did not need is the most avoidable spend in the whole exercise. Cancel them instead.
- Buying capacity on headcount. Channels are sized on simultaneous calls, not desks - see multi-line phone systems and channels.
A short budgeting checklist
- Pull three months of bills and list every line and standing charge.
- Walk the building and match sockets to charges. Flag anything unexplained.
- Get written quotes from your alarm and lift companies - these are your two unknowns.
- Ask your card provider whether your terminals dial out. Most no longer do.
- Check what connectivity is available at the address, and its install cost and lead time.
- Get the replacement priced per user, with the contract term and any mid-term increases stated in writing.
- Compare against your current bill including the 2026 increases, not last year's.
That last point matters more than people expect. Comparing a new quote against a pre-2026 legacy bill understates the saving, sometimes considerably - the WLR price rises have already moved the baseline.
The bottom line
Budget for a modest one-off project and an ongoing bill that is very likely lower than what you pay now. Put your contingency where the risk actually is - the alarm and the lift - and not in the phone line items, which are the predictable part. Then do it early enough that you are buying planned work rather than emergency work.
If you want this costed properly rather than estimated, send us your last bill and we will tell you what your lines actually are, what the replacement should cost and what the one-offs will be: get a no-obligation quote or call 0333 006 9399. We would rather tell you the audit saves you money than sell you lines you do not need.
Getting unknown calls on a business line? Our free UK phone number checker shows which network or provider Ofcom allocated any number to, and whether the range is in service — no sign-up.
Frequently asked questions
How much does the PSTN switch-off cost a business?
There is no single figure, because it depends entirely on what you have. As a guide: the phone side is inexpensive and usually reduces your monthly bill, while the one-off spend is concentrated in alarm signalling and lift emergency lines. A business with a handful of phone lines and no safety-critical kit can migrate for very little. A site with a monitored alarm and a lift should budget for specialist work from those contractors.
Will my phone bill go up or down after migrating?
For most businesses it goes down. Copper line rental disappears, UK calls are typically inclusive rather than per-minute, and features that used to be chargeable extras come as standard. The saving is larger the more lines you were renting, and larger again since legacy line rental rose through 2026.
Is there a grant or funding to help with the switch-off?
There is no general business grant for migrating phone lines - it is treated as normal replacement of a commercial service. Do not delay on the assumption that funding will appear. Where support exists it is generally aimed at vulnerable residential customers and telecare users rather than businesses.
What is the most expensive part of the PSTN switch-off?
Usually the lift emergency line, because it must keep working in a power cut and therefore needs a specialist unit and commissioning by your lift maintenance company. Monitored alarm signalling is the next largest. Both are third-party costs, so get them quoted early rather than assuming.
Does it cost anything to keep my phone numbers?
Porting is normally included by the gaining provider, though some charge a small per-number fee. If you have DDI ranges, ask specifically whether the charge is per number or per block - on a large range that difference is worth checking before you sign.
Can I save money by waiting until closer to the deadline?
No, it costs more. Legacy line rental has risen in stages through 2026, so every month waiting is a month at the highest price the old product has ever been. On top of that, alarm and lift engineers get scarcer as the deadline approaches, and late migrations tend to be provider-led and priced accordingly.
How do I compare quotes fairly?
Compare total monthly cost including connectivity, not just the voice line item, and make sure both quotes assume the same number of users and the same call inclusions. Ask for any mid-term price increases in pounds and pence, and check what the one-off charges cover - particularly whether porting, setup and training are included or extra.