Phone And Fax Number: Complete Guide

By Michael Chen · Published October 31, 2024 · Updated June 8, 2026 · 10 min read

Quick Answer: A phone number and a fax number look identical — both follow the standard 10-digit format — but they serve different purposes. A fax number connects to a fax machine or online fax service; a phone number connects to a voice handset. They can share a line with the right setup, or you can keep them completely separate using a virtual fax number.

You've seen contact blocks that list both a phone number and a fax number. They look the same. How are they different? Can one number do both jobs? And if you need a fax number for your business, how do you get one without buying a fax machine?

This guide answers all of those questions about phone and fax numbers — from the technical differences to the practical steps for setting one up today.

Phone Number vs. Fax Number: What Is the Difference?

A fax number and a phone number are technically the same thing. Both are assigned under the same North American Numbering Plan (NANP) — the 10-digit system used in the U.S. and Canada (area code + 7-digit local number). The same authority, the North American Numbering Plan Administrator (NANPA), overseen by the FCC, assigns both.

The difference is in what answers the call.

When a fax is sent to a fax number, the sending machine emits a CNG tone (Calling Tone — a 1100 Hz pulse every 3 seconds). The receiving fax machine or service responds with a CED tone (2100 Hz continuous). They then negotiate speed and begin transferring the document as audio-encoded data.

A voice phone call uses none of this. The two systems share the infrastructure — the same copper wires, the same fiber networks, the same numbering plan — but the devices on each end speak completely different protocols.

Can a Phone Number and Fax Number Be the Same?

Yes — but it requires deliberate configuration. One physical phone line can handle both voice and fax calls, using one of three methods:

Method 1: Distinctive Ring (DRPD)

Your phone company assigns a second number to the same physical line, each with a different ring pattern. A fax machine configured for DRPD (Distinctive Ring Pattern Detection) listens for its assigned pattern and only picks up when that pattern rings — ignoring voice calls.

How to set it up:

1. Contact your phone carrier and request a second number with Distinctive Ring (sometimes called "Teen Service" or a "secondary number")
2. Enable DRPD mode on your fax machine settings menu
3. Select the ring pattern assigned to the fax number

Limitations: Only works with physical fax machines that support DRPD. Not available from all carriers. Adds a monthly fee for the second number.

Method 2: Online Fax Service (Best for Most People)

An online fax service gives you a dedicated fax number hosted entirely in the cloud. Incoming faxes arrive as PDF email attachments — no fax machine answers the call, and your voice line is never occupied.

How to set it up:

1. Sign up with a service like mFax
2. Choose your fax number (local area code or toll-free)
3. Set your email address for incoming fax delivery
4. Start receiving faxes — completely separate from your voice line

Advantage: Your phone and fax are fully independent. No conflicts, no hardware, no shared-line headaches.

Method 3: Manual Answer Mode

The fax machine is set to receive only when you manually press a "receive fax" button. Works on any shared line — but requires someone to be physically present and paying attention. Not practical for unmonitored situations or after-hours faxes.

How to Get a Dedicated Fax Number

If you want a clean separation between voice and fax — which most businesses prefer — you need a dedicated fax number. Here are your options:

Option 1: Online Fax Service (Recommended)

The fastest and most affordable path. No hardware, no installation, no dedicated phone line.

Steps:

1. Choose a provider — mFax, eFax, MyFax, or similar
2. Create an account (takes under 5 minutes)
3. Select your number: local area code, toll-free (800/888/877), or international
4. Configure your email address for incoming fax delivery
5. Use the app or web browser to send faxes

Cost: $20–$50/month for most business plans. No hardware cost.

Best for: Most individuals, small businesses, healthcare providers, legal professionals, and anyone who needs occasional-to-moderate fax volume.

Option 2: Traditional Dedicated Phone Line

A separate physical landline from your local carrier, with a fax machine or multifunction printer connected.

Cost: $30–$80/month for the line + $100–$500 upfront for hardware.

Best for: High-volume environments with existing analog infrastructure, or industries where physical fax receipts are required.

Option 3: VoIP / T.38 Fax Line

Fax-over-IP using the T.38 protocol (the ITU standard for transmitting fax over the internet). T.38 compensates for the packet loss and jitter that breaks traditional fax over standard VoIP, making it reliable for fax use.

Cost: Typically $10–$30/month through a VoIP provider, plus a compatible VoIP adapter.

Best for: Businesses already using a VoIP phone system who want to add fax capability without a separate analog line.

What Is a Virtual Fax Number?

A virtual fax number is a standard phone number that is hosted in the cloud rather than tied to a physical phone line. When someone faxes it, the cloud service receives the transmission, converts it to a PDF, and delivers it to your email inbox or app.

You never need a fax machine, a dedicated phone line, or any hardware. The fax number is assigned to your account — not to a wire in a wall.

How virtual fax numbers work:

• Incoming faxes are received by the cloud service via T.38 or traditional PSTN connections
• The service converts the fax data to PDF or TIFF
• The file is emailed to you, available in a web portal, and optionally sent to your mobile app
• Outgoing faxes work in reverse: you upload a document, the service converts it and transmits it over the fax network

Key advantages over traditional fax lines:

• Accessible from any device — phone, tablet, computer
• No busy signal — cloud services queue incoming faxes automatically
• HIPAA-compliant options available with encryption and BAA
• Multiple users can share one account
• Fax history is stored and searchable

See our full guide to virtual fax numbers for a deeper look at how they work.

Local vs. Toll-Free Fax Numbers

When setting up a dedicated fax number, you choose between a local number (geographic area code) and a toll-free number (800, 888, 877, 866, 855, 844, or 833 prefix).

Toll-free fax numbers are ideal if your clients are spread across the country or if you project a national presence. They are also fully portable — if your business moves, the fax number moves with it.

Local fax numbers are better for brick-and-mortar businesses where clients expect a neighborhood presence (medical practices, real estate offices, law firms serving a single metro area).

What Happens When You Call a Fax Number?

If you accidentally dial a fax number from your regular phone, here is what you experience:

1. The line connects
2. You hear a high-pitched sustained tone — the CED tone (2100 Hz) — sometimes described as a screech or modem sound
3. Your phone does not emit the matching CNG fax tone in response
4. The fax machine detects no fax handshake
5. After 30–60 seconds, the fax machine disconnects

You cannot speak to anyone through a fax number. There is no voice capability on the receiving end — only fax-mode listening.

For virtual fax numbers: The behavior depends on the provider's configuration. Some play a recorded message ("This is a fax number — please send a fax"). Some simply disconnect. Neither allows voice communication.

Can You Use a Cell Phone Number as a Fax Number?

No — not natively. Here is why:

Cellular networks (GSM, LTE, 5G) use digital packet-based protocols optimized for voice and data. Traditional fax requires a continuous analog signal or T.38 IP fax protocol. Cellular carriers apply audio compression that destroys fax tone integrity. You cannot plug a fax machine into a cell phone, and even if you could, the signal would not survive the cellular network.

The solution: a mobile fax app with a dedicated fax number.

Apps like mFax, eFax, and others assign you a separate virtual fax number — distinct from your cell number. Your cell phone is just the device you use to access the service. The fax number itself lives in the cloud.

How it works:

1. Download the mFax app (iOS or Android)
2. Sign up — you are assigned a dedicated fax number
3. To send: upload a document, enter the recipient's fax number, tap Send
4. To receive: faxes arrive as PDFs in your app inbox
5. Your cell number is never exposed — the cloud fax number is what recipients see

This is the same workflow used by over 5 million mFax users who send and receive faxes entirely from their phones.

How to Find Someone's Fax Number

Fax numbers are not listed in a universal directory, but there are reliable ways to find them:

For verifying that an unknown fax number actually belongs to the intended recipient — important before sending sensitive documents — use a reverse fax lookup service. Since fax numbers are standard phone numbers, services like Whitepages and Spokeo can often identify the registrant.

See our full guide to fax number lookup for step-by-step instructions.

How to List Phone and Fax Numbers Professionally

When both numbers appear together on a business card, letterhead, or email signature, clarity and consistency matter.

Standard Abbreviations

Rule: Match your labels. If you use T: for phone, use F: for fax. If you use Phone:, use Fax:.

Business Card Layout Examples

Modern (compact):

T: +1 (415) 555-0123
F: +1 (415) 555-0124
E: name@company.com

Traditional (full labels):

Phone: (415) 555-0123
Fax:   (415) 555-0124

Email signature (one line):

p: 415.555.0123  |  f: 415.555.0124  |  company.com

Formatting Consistency

• Use the same punctuation style for all numbers (all dashes, all dots, or parentheses + dash)
• Include the area code on every number — 7-digit local-only formats are ambiguous
• For international distribution, use the E.164 format: +1 415 555 0124
• List the most important contact first (typically voice), fax second

See our detailed guide to fax number formats for complete examples including international formatting.

Why Industries Keep Phone and Fax Numbers Separate

Despite the availability of email and messaging apps, separate fax numbers remain standard in several industries:

Healthcare: Over 70% of healthcare communications still involve fax. Regulations and legacy EHR systems drive this. HIPAA-compliant fax (with encryption and BAA) is the accepted standard for sending PHI. Medical offices maintain separate fax numbers so patients and referral partners always reach the right channel. Learn about HIPAA-compliant faxing.

Legal: 93% of legal professionals report that fax remains necessary in their practice. Courts, opposing counsel, and government agencies accept faxed documents as formal submissions. A separate fax number provides a documented transmission record.

Real estate: Purchase contracts, disclosures, and addenda are routinely faxed between agents, title companies, and lenders. A fax number signals that the agent can handle the paperwork quickly.

Finance and insurance: Loan documents, claims forms, and signed authorizations still move by fax. Banks and insurers often require fax for paper-trail and authentication reasons.

Government: IRS fax numbers, court fax lines, and government agency numbers are all dedicated fax lines — never voice lines — to ensure reliable document receipt.

How to Port an Existing Fax Number to a New Service

If you already have a fax number and want to switch providers without changing the number, you can port it — the same way you'd port a cell phone number.

Key facts about number porting:

• Takes 1–6 weeks (most online fax services complete it in 2–4 weeks)
• Do not cancel your old service until the port is confirmed complete
• Verify the port will not inadvertently cancel DSL or other services bundled to the same line
• Most services charge a one-time porting fee or offer it free
• Your fax number remains unchanged — only the underlying service changes

See our full fax number porting guide for the step-by-step process.

Get a Fax Number Separate From Your Phone Number

The simplest path to a dedicated fax number in 2026 is an online fax service. No hardware, no installation, no dedicated phone line — and it works independently of your voice number from day one.

mFax gives you a dedicated fax number, delivers incoming faxes as PDFs to your email, and lets you send faxes from your phone in under 2 minutes. Over 5 million users fax this way.

For business teams, mFax Business adds virtual fax numbers for multiple departments, HIPAA compliance features, shared team inboxes, and delivery audit logs — starting at about $9/mo (billed annually). It's fully customizable: instead of fixed tiers, you build your own plan with a live calculator, choosing the exact number of seats and pages you need and paying only for what you use.