From my experience, every VoIP sales rep will tell you "porting usually takes 2 weeks". Every customer experience story online says it took 4-6 weeks. Somebody is lying. I pulled the data from 480 ports we have done since January 2024 and here is what the numbers actually say.
The raw data
480 ports across:
- 418 UK geographic numbers (01/02)
- 38 UK non-geographic (03)
- 14 freephone (0800)
- 10 shared cost (0845/0870)
Losing carriers: BT (231), Gamma (62), Vonage (38), 8x8 (22), TalkTalk Business (71), Sky Business (14), Virgin Media Business (28), other (14).
Median port completion times
| Number type | Losing carrier | Median | Worst 5% |
|---|---|---|---|
| UK geographic | BT | 7 working days | 21 |
| UK geographic | Gamma | 5 working days | 12 |
| UK geographic | TalkTalk Business | 10 working days | 34 |
| UK geographic | Sky Business | 14 working days | 42 |
| UK geographic | Virgin Media Business | 11 working days | 28 |
| UK non-geographic | any | 12 working days | 31 |
| Freephone (0800) | any | 18 working days | 45 |
So the honest answer: 5-14 working days for geographic numbers depending on who you are leaving. "Usually 2 weeks" is roughly right. "4-6 weeks" is usually because something went wrong.
What actually slows ports down
I sorted the outlier (>21 working days) cases by reason:
| Reason | % of slow ports |
|---|---|
| Account holder name mismatch on LoA | 38% |
| Address mismatch between LoA and losing carrier records | 24% |
| Losing carrier "cannot find" the account (usually misfiled by them) | 16% |
| Customer cancelled old service before port completed | 9% |
| Number range dispute (part of a DDI block vs individual) | 7% |
| Port rejected due to outstanding balance | 4% |
| Other / technical | 2% |
62% of slow ports are paperwork issues on the customer side. The other 38% are the losing carrier stalling.
The thing nobody tells you about porting from BT
BT has a process called "simultaneous provide" for new service + port at the same address. For existing sites, their standard port timeline is 7 working days, no drama.
However. BT's system requires the "account holder name" on the LoA to match the BT billing record EXACTLY. Including legal suffixes. If BT has you as "Widgets (UK) Limited" and the LoA says "Widgets UK Ltd", the port will fail at the automated check and a human has to re-key it. That is where the 21-day outliers come from.
Tip: get the losing carrier to email you the exact account holder name they have on file. Paste it verbatim into the LoA. This single step saves 2 weeks on about 1 in 5 ports.
Freephone ports are their own nightmare
0800 numbers port via a different process involving Ofcom's number administration. There are typically 2 intermediaries and it can legitimately take 6-8 weeks. If you are depending on a freephone port for a business launch, start 3 months early.
One of our retail customers had a 0800 port that took 52 working days in 2024. Their launch date was the day before the port finally completed. Not fun to manage.
What to ask the new provider to guarantee
- "Will you provide temporary numbers during the port window so we can test without moving real numbers?" (Good providers: yes, free.)
- "What happens if the losing carrier rejects the port — do you chase them or do I?" (Good: them.)
- "If my numbers are offline during the port window, what is your SLA for restoration?" (Good: <1 hour, with written commitment.)
- "Can I see a sample LoA before signing?" (If they say no, walk away.)
Honest advice
If you can wait 4 weeks, wait 4 weeks. If you can only wait 2, be prepared for possible slippage. If you absolutely cannot afford any outage, use the temporary-numbers-first approach and do not port until you have tested the new system end to end for at least a week.
DialPhone handles UK number porting end-to-end, chases the losing carrier on your behalf, and provides temporary numbers during the port window at no extra cost. Our median port time in 2025 was 6.5 working days.
