A business phone number is one of the few assets that appears simultaneously on your business cards, your website, your invoices, your Google listing, your contracts and in your customers’ memory. It is also one of the few you can lose permanently by checking one box at the wrong moment.
Porting is a right, mandated by the FCC, generally free, and technically routine. What makes it risky is not the procedure: it is the order of operations. Cancel before you port, and the number is gone.
This guide gives the actual process, the real timelines, and the six mistakes that cost a number.
What the rules actually say
Number portability is an FCC obligation that binds every carrier. Three principles follow, and they frame everything else:
- The number follows the user. It is not part of the carrier’s commercial offer: the carrier administers it, it does not own it.
- Porting is generally free. What gets billed is contract termination, not the port.
- The gaining carrier drives. You authorize the new provider, which then handles the request and the associated disconnection with the losing carrier.
That third point is the one everyone inverts, and it is the one that costs numbers.
Simple vs non-simple: the distinction that sets your timeline
The FCC defines two porting intervals, and the difference is not about how important you are — it is about the technical shape of the request.
| Simple port | Non-simple port | |
|---|---|---|
| Typical case | A single line, no switching complexity | Multiple lines, DID blocks, PRI, hunt groups, remote call forwarding |
| FCC interval | 1 business day | 4 business days |
| Who it applies to | Most consumer moves, some very small businesses | Almost every business with more than one number |
LOA and CSR: the two documents that decide everything
The LOA — Letter of Authorization — is the document you sign authorizing the gaining carrier to move your numbers. It carries the legal entity name, the service address, the account number and the list of numbers.
The CSR — Customer Service Record — is the losing carrier’s own record of your account. The gaining carrier requests it, and the losing carrier must return it within 24 clock hours, excluding weekends and its own holidays.
The port proceeds only if the two match exactly. Not approximately: exactly.
That is where most rejections come from, and they are almost always the same four:
- The legal entity name has changed — a merger, a rebrand, a conversion — and the carrier account was never updated.
- The service address is stale, because the company moved and only the billing address was corrected.
- The account number is wrong, often because someone used the billing account rather than the service account.
- The number list is incomplete, because a DID block was assumed to be included and was not.
Ask for the CSR before you sign anything. It is the losing carrier’s version of the truth, and it is the only document your port will be judged against.
Requesting your own CSR early — through the gaining carrier, or directly — turns a four-week guessing game into a one-week reconciliation. It is the single highest-leverage step in the whole process.
The process, in order
Inventory the numbers
Every number, including the ones nobody dials any more: the fax, the line for a closed department, the number in the equipment room. For each one: where it is printed — website, cards, vehicles, Google listing, contracts — and who uses it. A number you think is dead is often the one on marketing material still in circulation.
Pull the CSR and reconcile
Request the Customer Service Record and compare it line by line to what you will put on the LOA. Fix the mismatches before submitting, not after a rejection. This is the step that decides whether your port takes one cycle or four.
Sign the LOA with the gaining carrier
You authorize the new provider. It submits the request and handles the disconnection with the losing carrier. You do not contact your old carrier to cancel.
Build and test the target before the cutover
The new system is configured and tested on temporary numbers: routing plan, business hours, ring groups, greetings. Port day should be a switch, not a launch.
Port mid-week, never on a Friday
Schedule the cutover for a Tuesday or Wednesday morning, never a Friday or the day before a holiday. If a number does not come up, you want people available within the hour, not in three days.
Verify every number, one at a time
Call each ported number from a mobile outside your company network. Confirm it rings, reaches the right group, and that the caller ID you present on outbound is correct. That is the only check that proves the port actually worked.
The 6 mistakes that lose a number
1. Cancelling before porting
Mistake number one, and the only genuinely irreversible one. Cancelling severs the link between the number and an active account. The number returns to the pool, and in practice you will not get it back. There is no recovery process you can count on.
2. Treating a business port as simple
A multi-line business account is a non-simple port. Planning around a one-business-day interval, and telling the sales team the number will move overnight, produces a promise you cannot keep and a cutover nobody prepared for.
3. Mismatched account details
The LOA is compared against the CSR. A moved office, a merger, a changed entity name — each is a rejection, and each rejection costs a full cycle. None are serious individually; together they are how a two-week project becomes a two-month one.
4. Forgetting toll-free
Toll-free numbers do not port through LNP. They move by changing the RespOrg in the SMS/800 database — a different request, a different timeline, sometimes a different team at your provider. Companies routinely complete a flawless port of their local numbers and discover on cutover day that the 800 number was never in scope.
5. Porting before the target is configured
A number arriving on an unconfigured system rings into the void. Porting is the last step, not the first. The routing plan, hours and groups get designed beforehand — the method is in our business phone system guide.
6. Not checking outbound caller ID
Porting governs inbound calls. The number your team presents when dialing out is a separate setting on the new platform. Plenty of companies port their numbers correctly and then spend three weeks calling customers from an unrecognized number, with the predictable effect on answer rates — a problem we cover in why prospects don’t answer.
Special cases
Wireless numbers. Many carriers now require a port-out PIN or transfer PIN, set by the account holder, in addition to the account number. It exists to stop port-out fraud, and it is a common cause of a stalled business port when the person who set it has left the company. Retrieve it before you submit.
Numbers tied to an internet circuit. On bundled offers, porting the voice number can trigger the disconnection of the access circuit. Check this if the same link carries your connectivity — you do not want to lose internet on the day you change phone providers.
Partial DID blocks. A block of direct-inward-dial numbers is usually ported whole. If you only want part of it, say so up front: it is a technical constraint to settle before the request, not after.
Geographic eligibility. A number is tied to a rate center. Moving it to a provider without coverage in that rate center is not always possible. Confirm eligibility for every number before you plan a date.
What to take away
Porting is not a technical problem, it is a sequencing problem. Three rules keep you from ever losing a number:
Never cancel yourself. Pull the CSR and reconcile before you sign. Configure the target before you port.
Everything else — intervals, rejections for mismatched details, DID block constraints — is administrative back-and-forth: annoying, but reversible. Only early cancellation cannot be undone.
If your provider change is part of a broader migration, the full checklist is in our business VoIP guide, and the copper retirement timeline that is pushing many of these moves is in our guide to POTS line retirement.
