Last updated · Written for practice managers and office administrators.
What is changing
The copper telephone network that most fax machines plug into is being retired. AT&T told investors in December 2024 that it is “actively working to exit its legacy copper network operations across the large majority of its wireline footprint by the end of 2029.” Verizon and CenturyLink (Lumen) publish rolling copper retirement notices by state and wire center; both lists carry entries dated through 2026.
The rules are moving in the same direction. In March 2025 the FCC’s Wireline Competition Bureau waived, for two years, two of the conditions a carrier normally has to meet before it can discontinue a legacy voice service: the “stand-alone” requirement and the full Adequate Replacement Test. In plain terms, it is now easier for a carrier to get permission to switch off a copper voice product. Under 47 CFR § 63.71 the carrier still has to notify affected customers in writing, with the date of the change and the area affected, before it does so.
None of this switches off your fax number. A fax number is a telephone number; what disappears is the copper loop and the analog dial tone that a fax machine needs. The question for a practice is how to keep the number working once that dial tone is gone.
Your options
| Option | What it is | Where it fits |
|---|---|---|
| Keep an analog line | Stay on copper (or a carrier-supplied replacement voice service) and keep the machine. | Only where your carrier still offers it; it ends when the retirement notice for your area takes effect. Check with your carrier. |
| Adapter on an internet phone line | Plug the machine into a VoIP adapter and keep faxing over the internet. | Practices that must keep the physical machine. Whether faxes go through reliably depends on the adapter and the provider; check with your provider. |
| Online fax with your ported number | Move the number to a fax service; send from a browser or email, receive as PDFs. | Most offices. No line, no machine, no toner; the number stays the same for everyone who faxes you. |
The alternatives guide goes through cost, reliability and compliance for each. The rest of this page is about the third option, because it is the one where the number moves.
How porting works
Porting is the regulated process of moving a telephone number from one carrier to another. The FCC’s consumer guide puts the core rule simply: your old company cannot refuse to port your number, even if you owe money for an outstanding balance or termination fee. The interval is also set by rule — a simple wireline port must be completed within one business day of a complete request; a non-simple one within four business days.
- Check the number. The portability check identifies the carrier that holds the number and whether it can move. It is free and takes about a minute.
- Sign the authorization. The account holder with your current carrier signs a one-page Letter of Authorization online. Our carrier requires the letter to be signed within the last 90 days and to show the end user’s name and service address exactly as the losing carrier has them.
- Upload a recent bill. A bill from the current carrier dated within the last 30 days, showing the number and the account number.
- Wait for the confirmed date. Telnyx submits a simple port to the losing carrier within two business days and estimates about seven business days to completion; non-simple ports take fifteen or more.
- Keep the old line on. Cancelling early cancels the transfer. The old service closes once the number has moved.
The porting guide lists what AT&T, Verizon, Lumen, Frontier, Comcast, Spectrum and Cox each ask for, and the five reasons ports get rejected on the first try.
What to gather now
- The most recent bill for the fax line (dated within 30 days).
- The account number on that bill — it is not your online login.
- The name of the person your carrier lists as the account holder; that person signs the authorization.
- The PIN, passcode or “security code” your carrier prints on the bill, if it prints one.
- Whether the fax line shares an account with other phone lines or with DSL internet.
Guides in this series
- The copper line shutdown — the FCC orders, the carrier timelines, and what to do before the notice.
- Replace the fax machine and keep the number — the switch, in order.
- Port a fax number — per-carrier requirements, timelines, rejections.
- Fax line alternatives — analog line, adapter, or online fax.
- Toll-free fax numbers — 800-series numbers and RespOrg transfers.
- Receive faxes by email — notifications, storage, team inbox.
- Send large faxes — 100+ pages, scheduling, receipts.
Plans and the free-porting rule are on the pricing page. Questions about a specific line: support@usfax.com.