350,000 business lines still on copper — and Ofcom's rules say every number can be kept

The UK phone network has 139 days left, and the migration maths still looks uncomfortable: when Openreach last updated the industry in July, about 1.5 million lines were still running on legacy copper — down from 1.9 million in June — and roughly 350,000 of the premises involved are businesses. Buried in the regulator's rulebook, though, is the part that decides whether all this upheaval costs a company its identity: your number is portable, and your provider cannot directly charge you to release it.

The four porting guarantees most firms never hear about

Ofcom's General Condition C7 is the UK's switching rulebook, and it is written into every provider's licence. The clauses that matter when a business number is on the line:

• C7.6(a) — number porting must be provided on reasonable terms and conditions.
• C7.6(b) — you can port your number for at least one month after you have switched or cancelled. Miss the coordination date and there is still a rescue window.
• C7.6(c) — you must not be directly charged for porting your number.
• C7.7(c) — if a port fails part-way through, the number and its services must be reactivated until the process completes. A botched port should never leave a business dark.

Why the fine print matters more in the final months

Openreach has been blunt that there is no extension to the 31 January 2027 deadline, and it has previously stated that legacy copper line prices are set to double by October 2026 — so staying put is no longer the cheap option either. With engineering capacity tight, firms that port early get a calm, coordinated cutover; firms that wait get queues. The one-month window in C7.6(b) is a safety net, not a migration plan. Our PSTN switch-off guide covers the line audit that should come first.

Porting without downtime

1. Inventory before touching contracts. List every number, what it rings on, and which provider holds it.
2. Port instead of cancelling. A surrendered number can be lost for good; a ported one keeps working. Porting a number to DIDcomms turns it into a virtual number that forwards to mobiles, desk phones or SIP — no copper involved.
3. Give it a home. Free PAYG covers light use, while a £9.97-a-month plan adds a bundled minute allowance and ten concurrent calls.

Related: 141 days left on the PSTN · What is a DID number?