PSTN switch-off countdown 2027: what every UK SMB must do in the next 12 months

On 31 January 2027, BT Openreach retires the UK Public Switched Telephone Network — every analogue line, every ISDN circuit, every WLR2 wholesale product. If your phones plug into a master socket today, they stop working in 18 months.

Who is at risk

Roughly 2 million UK SMBs still run analogue lines, plus lift phones, alarm panels, EPOS terminals dialling for card auth, and fax machines in healthcare. Every one of these needs a replacement signed off before the cut-over.

The 6-month rollout calendar

1. Month 1 — audit. List every line, including ancillary devices. Note their DDIs and contract end-dates. Free template at our WLR2 FAQ.
2. Month 2 — choose. Hosted VoIP (Silux Call) vs SIP-trunk-plus-PBX. We cover both at VoIP vs SIP trunk.
3. Month 3 — port. Submit STAC (landline) or PAC (mobile) codes. Free porting on Plus and above; typical cut-over is 24 hours.
4. Month 4 — run in parallel. Keep both providers live for at least 7 days. Test every IVR branch, every hunt group, every recording flow.
5. Month 5 — switch ancillaries. Lift phones, alarm panels, fax. Replace with IP-native or wrap with an ATA + battery backup.
6. Month 6 — decommission. Cancel the BT line, keep the cancellation email, file with your accountant.

What it costs

For a 10-user UK SMB on Silux Call Plus (£11.95/user), expect £1,434/year subscription plus £0-£30 one-off porting. Ancillary device migration ranges £50-£400 per endpoint depending on age. Most SMBs pay back the project within 6-9 months versus their old WLR2 bill.

The biggest mistake

Leaving porting to December 2026. Openreach's order book will be saturated. Port at least 6 months before the cut-over.