How number porting actually works
Porting moves a number from your old carrier to your new one, and the two carriers run the process between them.
Who actually runs the port?
Porting moves a phone number from the carrier you are leaving to the carrier you are joining. Your new provider submits the request; you authorize it with a letter of authorization. The two carriers then validate, agree a date, and switch the number over. You are a signatory, not a participant, for most of it.
| Party | Role | What they control |
|---|---|---|
| Losing carrier | The provider you are leaving | The customer service record every detail is checked against, and whether to accept or reject |
| Gaining carrier | The provider you are joining | Submitting the request, correcting rejections, and proposing a port date |
| You | The account holder | Signing the letter of authorization, and keeping the old account open and paid until it is done |
What happens after you sign
The request is submitted
Your new provider sends the number list, your account details and the signed letter of authorization to the losing carrier.
The losing carrier validates it
Every field is compared against their customer service record. A mismatch anywhere comes back as a rejection rather than a question.
A port date is set
Once validation passes, the carriers agree a date and usually a window within it. Treat it as firm only when your provider confirms it in writing.
The number cuts over
On the day, calls stop arriving on the old service and start arriving on the new one. This is not always instant across every network.
You test, then cancel
Call every number from an outside line. Only when all of them answer correctly do you close the old account.
What limits where a number can go
- Geography. A number normally ports only within the same rate center, so a number can follow you across town but not usually across the country.
- Number type. Toll-free numbers run on a separate process from geographic numbers and are handled differently.
- Account state. A pending order or a port-out lock on the losing account will stop the request. An unpaid balance often shows up as a rejection reason too, though FCC guidance is that your old provider should not refuse to port a number simply because you owe it money — it can still bill you for the balance.
- Ownership. A number that came bundled with a service may never have been contractually yours to move.
Why the date can move
A scheduled port date is an agreement between two companies, and either of them can raise an issue against it. A late-surfacing mismatch, a freeze on the account, or a capacity problem at either end can push the date. That is normal, and it is why you should not schedule the phone installer, print new stationery, or end the old contract against an unconfirmed date.
The regulated part of this is short. FCC rules generally give carriers one business day to complete a simple port and four business days for a non-simple one, once a valid, accurate request has been accepted. The weeks a business experiences come from the steps around that clock: gathering paperwork, failing validation, waiting for a scheduled date. The cutover itself is quick.
If you are still deciding whether to move your numbers at all, start with keeping your phone numbers. It covers the choice and the paperwork you will need to collect.
Processes and timelines vary between carriers and number types. Use this as a map of the shape of the process, and rely on your gaining provider for what applies to your specific port.
Last reviewed September 12, 2026
