Keep your number

Replace the fax machine.
Keep the same number.

The fax number on your letterhead can outlive the machine and the phone line it plugs into. This is the order of operations, written so an office manager can run it in an afternoon and a week of waiting.

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Last updated · Written for practice managers and office administrators.

Why the number can move without the machine

A fax machine is a modem on an ordinary telephone line. The number belongs to the line, not to the machine, and federal number-portability rules apply to it like any other local number: the carrier must port it on request and may not refuse because of an unpaid balance or a termination fee. Simple wireline ports must complete within one business day of a complete request under 47 CFR § 52.35; the rest of the calendar is validation and scheduling.

When the number moves to usfax, our carrier (Telnyx) becomes the carrier of record. Inbound calls to the number terminate on our fax servers instead of your wall jack; the page images are converted to PDF and appear in your inbox. Outbound faxes are sent with the same number as caller ID.

The order of operations

  1. Find the bill. You need the most recent invoice for the fax line, dated within the last 30 days. It carries the three things the losing carrier validates: the account number, the name of the account holder, and the service address exactly as they have it.
  2. Run the portability check. It tells you which carrier holds the number and whether it can move. If the number was assigned to you by an online fax service, this is where you learn whether that provider will release it.
  3. Choose a plan. Porting is free on Solo, Practice and Multi-site. Pick by pages per month and number of users; the pricing page has the full table.
  4. Sign the Letter of Authorization. The person named on the carrier account signs it online. Telnyx requires the signature to be within the last 90 days and every number being ported to be listed.
  5. Enter the account number and PIN. Each carrier has its own format; the porting guide lists them. A wrong PIN is the most common cause of delay Telnyx reports.
  6. Wait for the confirmed date. You get a firm order confirmation (FOC) date from the losing carrier. Telnyx activates the number on that date, during business hours Monday to Friday.
  7. Test, then cancel. Send yourself a test fax after activation. Only then cancel the old line.

What changes for staff

Before and after replacing the fax machine
TaskWith the machineAfter the switch
Incoming faxPaper in the tray; someone walks it to a desk.Email notification with a link; the PDF opens in the inbox. Route by sender to the right person.
Outgoing faxPrint, feed, dial, wait by the machine.Upload the PDF or send from email; delivery confirmation arrives when the receiving machine confirms every page.
Proof of deliveryTransmission report from the machine, if someone kept it.A one-page delivery receipt per fax, downloadable any time it is in your history.
RecordsFiling cabinet.Documents kept for the retention period you choose (7 days to unlimited); fax history kept 12 months by default, up to 72.
Consumables and line rentalToner, paper, the phone line, the maintenance contract.The subscription. No line, no hardware.

How long it takes

Telnyx submits a simple port to the losing carrier within two business days and estimates about seven business days from submission to completion. A non-simple port — a line that shares an account with other numbers, a line carrying DSL, or a business account with special features — is submitted within four business days and takes fifteen business days or more. The FCC floor underneath those estimates is one business day for a simple port and four for a non-simple one; the difference is the carrier’s queue and the scheduling of a port date.

Two things you can do to keep to the short end: match the name and address on the bill character for character (“Suite 200” and “STE 200” are different to a carrier’s system), and tell us up front if there is a pending order or a freeze on the account, because either one produces a rejection.

What to do with the machine

Once the number has moved, the machine has no line. If a device in the office must fax on its own (older diagnostic equipment, for example), keep a separate line for that device or put it on an internet phone adapter — see fax line alternatives. Otherwise, the machine has a memory: clear it before disposal, since many models keep the last pages sent and received.

If your practice handles protected health information, one more note. A HIPAA Business Associate Agreement is coming free to every paid plan and will be signed by you in Settings → HIPAA BAA. Until you have signed it, your account is not covered by a BAA and must not be used for PHI. Details are on the HIPAA-ready fax page.

Frequently asked questions

No. They dial the same number. On port day the number stops ringing the machine and starts arriving in your usfax inbox as a PDF. Outgoing faxes show your ported number as the caller ID, so replies come back to the same place.

Not on the same number. Once the number has moved, the old line no longer carries it. If you want a machine for a specific device (some lab equipment, for example), keep a separate line for it, or use a VoIP adapter — see the fax line alternatives guide.

Only after the port has completed and you have received a test fax on the new service. Cancelling before the port completes cancels the port, because a disconnected number cannot be moved. Your carrier's final bill and any contract termination charge are unaffected by the port itself.

A number cannot move while other services ride on the same loop. Move or cancel the DSL service first, then port the number. CenturyLink lists loops carrying broadband among the ports it does not treat as simple; other carriers handle it similarly. Check with your carrier.

No. That is the point of porting. Referral pads, letterhead, payer directories and the number on file with your suppliers all stay valid.

Keep your fax number

Enter the number and we check whether it can move, which carrier holds it, and what your carrier will ask for. Free, takes about a minute, no card needed. Porting is free on every subscription plan.

Run the free portability check

Sources

Facts about carriers, regulators and competitors on this page come from the documents below, read on the dates shown. Carrier rules change; when a detail matters for your line, check with your carrier.

  1. Keeping Your Telephone Number When Changing Service Providers (consumer guide) Federal Communications Commission, accessed September 8, 2026.
  2. 47 CFR § 52.35 — Porting intervals Cornell LII (eCFR text), accessed September 21, 2026.
  3. Porting requirements (LOA, invoice, PIN) Telnyx, accessed September 8, 2026.
  4. Porting policy and procedure (timelines) Telnyx, accessed September 8, 2026.
  5. Number porting rules and guidelines (rejections, FOC validity) Telnyx, accessed September 8, 2026.
  6. CenturyLink wholesale Local Number Portability product catalog CenturyLink / Lumen, accessed September 8, 2026.
  7. usfax.com Terms of Service (cancellation, refunds, porting) usfax.com, accessed September 21, 2026.
  8. usfax.com Pricing usfax.com, accessed September 21, 2026.