PSTN Switch-Off: A 90-Day Countdown Checklist for Businesses

With 90 days left before your PSTN or ISDN line stops working, the priority order is: confirm exactly what's still running on the old network, choose and order your replacement system, get numbers ported early, and test everything well before the final cutover date. Openreach has confirmed the national switch-off date of 31 January 2027 won't be pushed back again, so leaving this until the last few weeks isn't a realistic option for any business still on legacy lines.

Why 90 Days Matters

Ninety days sounds like plenty of notice, but it disappears quickly once you factor in choosing a system, porting numbers — which alone can take one to two weeks per number — installing and testing equipment, and training staff. Businesses that start with 90 days in hand typically have a calm, well-tested migration. Businesses that start with two weeks tend to have a stressful one.

Use our PSTN switch-off checker first if you're not sure exactly what's still running on copper at your premises.

90 to 60 Days Before: Audit and Decide

• List everything connected to a PSTN or ISDN line — this is rarely just phones. Alarm systems, card machines, lift lines, fax machines, and door entry systems often run over the same old copper network and get missed in planning.
• Check your current contract end date, since some providers set their own earlier deadlines than the national one.
• Decide on a replacement system. Common options include Gamma Horizon, 3CX, or Microsoft Teams Calling — each suits different business types, so it's worth comparing rather than defaulting to whichever one you've heard of.
• Check your broadband is ready. A VoIP-based system depends entirely on your internet connection, so it's worth confirming your bandwidth and reliability can support it before committing to a go-live date.

60 to 30 Days Before: Order and Prepare

• Place your order for the new system, including any handsets, headsets, or ancillary hardware.
• Submit number porting requests now, not later. Porting typically takes one to two weeks, but delays happen — starting early builds in a buffer. Our guide to how long porting takes covers this in detail.
• Arrange replacements for any non-phone equipment still relying on the old lines — alarm systems and card machines in particular often need a specific digital alternative, not just a general internet connection.
• Confirm emergency calling will be configured correctly on the new system, particularly if you operate from more than one site. Our guide to 999 calls on VoIP explains what's required.

30 to 14 Days Before: Install and Test

• Get the new system installed ahead of your existing service ending, so there's a genuine overlap rather than a hard cutover with no fallback.
• Test calls thoroughly — inbound, outbound, internal transfers, and any auto attendants or call queues.
• Test any equipment that was moved across, such as alarm systems or card machines, rather than assuming it works because it's now plugged in.
• Plan for power resilience. Unlike a traditional line, VoIP stops working in a power cut unless you've got a backup in place — our guide to what happens to your phone system in a power cut covers the options.

14 to 7 Days Before: Train and Communicate

• Train staff on the new system, particularly anything that behaves differently — call forwarding, voicemail, or how to use a new app or handset.
• Update any documentation, call scripts, or signage referencing old extension numbers or dialling instructions if these have changed.
• Confirm your cutover date and time internally, so everyone knows what to expect and who to contact if something doesn't work as planned.

Switch Day and Immediately After

• Don't cancel your old line until the new system's confirmed working. This is the single most common mistake in any migration, not just PSTN switch-off — always keep a fallback active until you're certain the new setup is solid.
• Test again on the day itself, since live traffic sometimes surfaces issues a pre-go-live test didn't catch.
• Keep a short list of who to contact at your new provider if anything needs fixing quickly in the first few days.

Frequently Asked Questions

What actually happens on 31 January 2027? Openreach permanently withdraws the PSTN and all Wholesale Line Rental products. Anything still running on analogue or ISDN lines at that point stops working, with no further extension planned.

Do I need to migrate everything by the same date? The final national deadline is 31 January 2027, but some providers set their own earlier cut-off dates for their customers, so it's worth checking your specific contract rather than assuming you have until the last possible day.

What if I'm not sure what's still running on PSTN at my premises? Start with our PSTN switch-off checker, and physically check any equipment that's been in place for years without anyone questioning what it's connected to — alarm and card payment systems are the most commonly forgotten.

Is 90 days really necessary, or can this be done faster? It can be done faster if needed, but 90 days gives realistic breathing room for porting delays, equipment lead times, and proper testing — rushing a migration is when things get missed.

Leaving a PSTN migration to the final weeks is the most common — and most avoidable — mistake businesses make. Request a quote for a straightforward migration plan, or use our PSTN switch-off checker to see exactly where you stand.