Verified against Ofcom Connected Nations Spring 2026, IASME Cyber Essentials April 2026 standard and current operator pricing.
Quick answer: Porting a UK phone number to a VoIP provider takes 10 working days standard, 1–3 days express. You sign a Porting Authorisation Form (PAF/LOA), the new provider submits it to Openreach or the carrier holding the number, and on porting day the number switches platform during a ~30-minute overnight window. Costs are £10–£25 per number standard or £50–£150 per range express — usually waived on contracts of 24+ months. Keep your provider engaged, check the PAF carefully, and don’t cancel the old line until the port confirms successful.
How VoIP porting works behind the scenes
You sign PAF
The Porting Authorisation Form lists the numbers and authorises the new provider to claim them.
New provider submits
They lodge the request with Openreach (or the losing carrier) via the OTA2 portal.
10-day window
The losing carrier validates ownership, agrees a port date, confirms back.
Port day
Number switches platform overnight in a 30-min window. Calls follow the new route from then on.
What you need to provide your new VoIP provider
- The numbers to port — full 11-digit format with prefix (e.g. 02079460000).
- Most recent BT/carrier bill — proves you own the numbers.
- Account number with losing carrier — usually on the bill.
- Service postcode — must match what the losing carrier has on file.
- Authorised signatory — director, named contact, or any person with billing authority.
- Preferred port date — pick a Tuesday or Wednesday at 06:00 to minimise risk.
- Single-line vs multi-line — single ISDN30 ranges port as a block, single PSTN lines individually.
What can go wrong (and how to avoid it)
Common rejection reasons
Why ports get bounced and re-quoted.
Avoid by:
- Address mismatch — match the bill exactly
- Wrong account number
- Number actually belongs to landlord, not you
- Account in dispute / unpaid
- PAF signature not director-level
What “stuck” looks like
Symptoms when a port is delayed or partially live.
Diagnose:
- Inbound calls reach voicemail not your phones — port not yet live
- Outbound CLI shows wrong number — port live, CLI not updated
- Some calls reach old line, some new — fall-back routing during transition
- Engaged tone for hours — escalate to OTA2
Switch to a smarter phone system
Hosted VoIP from £12/user/month with free number porting. Get a no-obligation quote in 60 seconds.
Or call us on 0333 015 2615
Costs by number type and volume
| Number type | Per number | Per range (10 nos.) | Express (1–3 day) |
|---|---|---|---|
| Geographic 01/02 | £10–£15 | £25–£40 | +£100 |
| Non-geo 03 | £15–£25 | £40–£60 | +£150 |
| Freephone 0800 | £25–£50 | — | +£200 |
| Premium 084 / 087 | £25–£75 | By case | By case |
| Mobile (07) | — | — | Use STAC code; not “porting” in this sense |
Setting up the port — step by step
- Day 0
Quote & PAF signed
New provider provides quote and PAF; you sign and return with bill copy.
- Day 1–2
New provider submits via OTA2; losing carrier acknowledges within 48 hours.
- Day 3–4
Carrier validation
Losing carrier checks ownership, address match, account standing. Rejections (if any) come here — fix and resubmit.
- Day 5–7
Port date confirmed
Losing and gaining carriers agree exact port date and time (usually overnight).
- Day 8–9
Pre-port testing
New provider provisions the numbers on test extensions. You can validate routes before go-live.
- Day 10 · 06:00
Port live
Numbers switch platform; verify by calling from outside; cancel old service only after 7+ days of stable inbound calls.
Tips for keeping calls flowing through port day
Pre-stage everything
New phones provisioned and tested 1 week before port. Don’t leave any “we’ll do it on the day” tasks.
Keep the old line for 30 days
Pay the rental for one extra month — gives you a fall-back if anything goes wrong on day 10.
Monitor inbound from outside
Have one staff member ring your main number from a mobile every 15 minutes during the switchover window.
Communicate downtime
Email customers a heads-up: “We’re upgrading our phones — if you can’t reach us between 6am–7am Tuesday, please email.”
Porting numbers to a UK hosted VoIP provider?
We manage 200+ ports a month — including emergency ports when an existing provider goes bust. Free porting on 24-month contracts.
VoIP number porting — FAQs
Yes — once the number is on a hosted VoIP platform, you can install the provider’s mobile app on your phone. Calls to your business number ring both the desk handset and the app.
The new provider gets a rejection code (e.g. “address mismatch”, “account in dispute”). They fix the issue and resubmit, usually within 1–2 days. Most resubmissions succeed.
Yes — the same OTA2 process applies whether you’re leaving BT, Vodafone, Gamma, hypercloud or any other UK carrier. Inter-VoIP ports often complete faster (5–7 working days).
Yes — voicemail platforms don’t transfer. Download any retained messages before the port date.
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