By David Thompson · Published April 14, 2025 · Updated June 8, 2026 · 10 min read
Quick Answer: A fax header is the line of text automatically printed in the margin of every outgoing fax page — showing your name, fax number, and the date/time. US federal law (TCPA) requires it on every transmission. To configure it: go to your fax machine's Menu → Initial Setup → Station ID, or find the sender settings in your online fax service account.
Every fax you send carries a small strip of identifying information across the top or bottom of the page. Most people never notice it — until they get hit with a compliance complaint for sending faxes without one.
That strip is the fax header. It's generated automatically by your fax machine or service, it appears on every page of every transmission, and under US federal law, it is not optional. Getting it wrong — or leaving it as the factory default — exposes your business to penalties of up to $1,500 per fax.
This guide explains exactly what a fax header is, what it must contain, how it differs from a fax cover sheet, and how to configure it correctly on traditional fax machines and modern online fax services.
What Is a Fax Header?
A fax header is a compact strip of sender identification automatically printed in the top or bottom margin of each transmitted fax page. It functions like a return address — except instead of being hand-written, it's machine-generated from settings programmed into your device or account.
Unlike a fax cover sheet, which is a full separate page that the sender manually prepares, the fax header:
- Appears in the narrow margin of the page — not as a full page
- Is generated automatically without any action from the sender
- Repeats on every page of the transmission
- Contains only compact identifying data (not a message or instructions)
The header is pulled from your machine's "Station ID" or your online fax service's sender settings. Once configured correctly, it prints on every outbound fax forever — no extra steps required.
Where does the header appear?
The TCPA specifies "a margin at the top or bottom of each transmitted page of the message or on the first page of the transmission." In practice, most fax machines and services print the header at the very top of each page, above the document content, in a narrow strip approximately 5–10mm tall.
Why Fax Headers Are Required by Law
The fax header is not a courtesy feature — it's a federal legal requirement in the United States.
The Governing Law: 47 U.S.C. § 227(d)
The Telephone Consumer Protection Act (TCPA), at Section 227(d)(1)(B), states:
"It shall be unlawful for any person within the United States to use a telephone facsimile machine, computer, or other device to send an unsolicited advertisement to a telephone facsimile machine unless… the telephone facsimile machine or other device used to send the advertisement clearly marks, in a margin at the top or bottom of each transmitted page of the message or on the first page of the transmission, the date and time it is sent and an identification of the business, other entity, or individual sending the message and the telephone number of the sending machine or of such business, other entity, or individual."
The FCC's implementing rule (47 CFR § 68.318(d)) extends this to all commercial fax senders and adds: if a third-party fax broadcasting service supplies the recipient list, that broadcaster's registered business name must also appear on the fax.
The Three Mandatory Elements
Every outgoing fax must show all three of the following:
| Required Element | What It Means |
|---|---|
| 1. Date and time | The date and local time the fax was transmitted |
| 2. Sender name | The registered business name, legal entity name, or individual's name |
| 3. Telephone number | The fax machine's number or the sender's main telephone/fax number |
Page count is not legally required in the header — but it's strongly recommended on a cover sheet for multi-page documents.
Penalties for Non-Compliance
Missing fax header information is treated as a TCPA violation — the same category as sending unsolicited junk faxes:
| Violation | Penalty per Fax |
|---|---|
| Missing header identification | Up to $500 per page/transmission |
| Willful or knowing violation | Up to $1,500 (treble damages) |
| FCC civil enforcement | Up to $11,000 per fax |
A single fax blast to 1,000 recipients without proper header identification can carry $500,000 in statutory damages — before trebling. Private plaintiffs can sue under the TCPA's private right of action without waiting for the FCC to act.
Healthcare adds another layer
For healthcare organizations, an inaccurate or missing fax header timestamp also undermines the PHI audit trail required under HIPAA. Learn more about HIPAA-compliant faxing and the specific rules that apply to medical fax transmissions.
Fax Header vs. Fax Cover Sheet
The fax header and the fax cover sheet are often confused — they serve related but distinct purposes:
| Fax Header | Fax Cover Sheet | |
|---|---|---|
| Location | Top/bottom margin of each page | Separate first page |
| Generation | Automatic (machine or service) | Manual (sender creates it) |
| Frequency | Every page of every transmission | Once per transmission |
| Content | Name, fax #, date/time — compact ID only | Recipient info, subject, message, page count, confidentiality |
| Legal obligation | Required by TCPA for sender ID | Required for HIPAA PHI faxes; best practice elsewhere |
| Character limit | Typically 20–21 characters for name field | No limit |
| Customization | Very limited | Highly flexible |
The practical rule: use both. The header handles compliance; the cover sheet handles communication. A fax without a cover sheet can still be legally valid — a fax without a proper header cannot.
What Should a Fax Header Contain?
Beyond the three legally required elements, professional fax headers often include additional information:
Legally required:
- Date and time of transmission
- Sender name (business or individual)
- Sender telephone number
Recommended best practice:
- Recipient's fax number (helps identify misdirected faxes)
- Page number / page count (e.g., "Page 2 of 5")
Optional but common:
- Company address
- Email address or website
- Subject/reference line (if the service supports it)
One critical constraint: most fax machines and services limit the name field to 20–21 alphanumeric characters. "Acme Professional Legal Services Group LLC" will be truncated to "Acme Professional Leg" — which can make identification ambiguous. Use an abbreviated form of your business name that fits and is still recognizable.
How to Set Up a Fax Header
On a Traditional Fax Machine
The process is similar across all major brands — you're configuring the machine's "Station ID," which drives both the visible fax header and the TSID (Transmitting Subscriber Identification) broadcast during the T.30 protocol handshake.
Enter the machine's menu
Press the Menu or Setup button on your machine's control panel. Navigate to Initial Setup, Fax Settings, or User Settings — the exact path varies by manufacturer.
Find Station ID or Fax Header settings
Look for an option called Station ID, Fax Header, Sender ID, or Unit Name depending on your brand:
- Brother: Menu → Initial Setup → Station ID
- Canon: Settings → Register → Unit Telephone Number / Register Unit Name
- HP / Epson: Fax Setup → Advanced Setup → Fax Header (or use the Fax Setup Wizard)
Enter your fax number
Input your complete fax number, including area code. For US numbers, include the country code (e.g., +12125550100). Most machines accept up to 20 digits. This number becomes the "telephone number of the sending machine" required by TCPA.
Enter your name or business name
Type your registered business name or individual name (up to 20–21 characters). This is the "identification of the business, entity, or individual" required by TCPA. Keep it short, accurate, and matching your registered business records.
Verify and set the machine clock
The date and time in your fax header come from the machine's internal clock — not from a field you configure. Go to the clock/time settings and verify:
- Correct date (year, month, day)
- Correct time (with AM/PM or 24-hour format)
- Correct time zone (if the machine supports it)
An incorrect clock means every fax timestamp is wrong — a serious compliance and evidentiary problem.
Send a test fax to verify
Send a test fax to your own fax number or email (if your service supports fax-to-email). Inspect the received fax to confirm the header shows: your name, your fax number, and the correct date/time. If anything is wrong, return to the Station ID settings.
After a power outage
Many older analog fax machines lose their clock settings during a power outage. After any extended power interruption, verify the date/time before sending — a wrong clock can invalidate every timestamp on outbound faxes until it's corrected.
On an Online Fax Service (mFax)
Online fax services configure header information through your account settings — no menu navigation required. The service automatically populates the header on every outbound fax based on your saved profile.
For mFax Business users:
- Log in at app.mfax.to
- Navigate to Account Settings → Profile or Sender Information
- Enter your registered business name and your fax/phone number
- Save — your header is now configured for all outbound faxes
The date and time are automatically applied from server time with your account's timezone settings, so you don't need to worry about a clock drifting out of sync.
Try mFax Business — HIPAA-ready faxing with automatic header compliance, delivery tracking, and virtual fax numbers from about $9/mo (billed annually).
For other services, the pattern is similar: look for Sender Settings, Account Details, Profile, or Fax Settings in your account dashboard. The fields will ask for your name/company name and phone number — fill both in, save, and the service handles the rest.
On Windows Fax and Scan
If you're using Windows's built-in fax feature with a fax modem:
- Open Windows Fax and Scan → Tools → Sender Information
- Enter your name, fax number, and address
- The date/time is pulled automatically from your system clock (Windows time settings)
Ensure your Windows clock is synced to an internet time server (Settings → Time & Language → Sync now) to keep timestamps accurate.
What Is a TSID? (And Why It Matters)
When your fax machine connects to the recipient's machine, the two devices exchange identification strings as part of the T.30 protocol handshake — before any document data is transmitted. These identifiers are:
- TSID (Transmitting Subscriber Identification): Sent by your machine — identifies the sender. Contains your fax number and optionally your name. This is what drives your fax header.
- CSID (Called Subscriber Identification): Sent by the recipient's machine back to yours — identifies the receiver. Your fax activity log records this.
The TSID appears in two places: (1) in the visible fax header printed on the received document, and (2) in the recipient's fax activity log. Configuring your Station ID is the same as configuring your TSID — the terms are used interchangeably.
For IT administrators managing a fax server or multi-user fax system, the TSID can sometimes be configured separately from the visible header — allowing different identifiers for the protocol handshake vs. the printed header. In most business contexts, keeping them consistent is both simpler and more defensible from a compliance standpoint.
To understand more about how fax machines communicate at the technical level, see our guide on how a fax works.
Common Fax Header Mistakes to Avoid
1. Leaving the factory default
Many fax machines ship with generic headers reading "FAX," the model number, or a string of zeros. These factory defaults do not satisfy the TCPA identification requirement. The first thing you should do with any new fax machine or online fax account is configure the header.
2. Using an outdated name or number
When your business changes its name, phone number, or fax number, update every device and account where a fax header is configured. Old identifiers in fax headers create compliance ambiguity and make follow-up impossible for recipients.
3. Not verifying the clock
The date/time stamp in a fax header is only as accurate as the machine's internal clock. Verify it on initial setup and after any power outage. For online services, verify your account's timezone setting matches your actual location.
4. Assuming the header replaces the cover sheet
The header satisfies the legal identification requirement. It does not replace the communication function of a cover sheet — telling the recipient who the fax is for, what it's about, and how many pages to expect. Use both.
5. Exceeding the character limit
At 20–21 characters, the name field is tight. Test what gets truncated by sending a fax to yourself. A truncated business name can make your identification ambiguous — potentially triggering a TCPA violation even if you technically configured the field.
6. Ignoring the opt-out notice for marketing faxes
The fax header alone is not sufficient for unsolicited fax advertisements. The Junk Fax Prevention Act of 2005 also requires a visible opt-out notice on the first page of any fax ad — including a domestic phone number and fax number for opt-out requests, available 24/7, honored within 30 days. Learn more about junk fax rules and how to stay compliant.
7. Sending from someone else's machine
If you send a fax from a colleague's or client's physical fax machine, their header — not yours — will appear on the transmitted document. This can cause identity confusion and compliance issues if the machine's header is configured for someone else.
Fax Header Setup: Quick Reference
| Scenario | Where to Configure |
|---|---|
| Brother fax machine | Menu → Initial Setup → Station ID |
| Canon fax machine | Settings → Register → Unit Telephone Number / Unit Name |
| HP / Epson fax machine | Fax Setup → Advanced Setup → Fax Header |
| Windows Fax and Scan | Tools → Sender Information |
| mFax Business | app.mfax.to → Account Settings → Profile |
| eFax | eFax Portal → Account Details → Profile |
| RingCentral Fax | Admin Portal → Users → Outbound Fax Settings |
| Any online fax service | Account → Settings → Sender / Profile information |
Send Compliant Faxes Without the Setup Headache
Modern online fax services like mFax handle header compliance automatically — no Station ID menus, no clock sync worries. You enter your name and number in your account profile once, and every fax you send carries the correct header indefinitely.
For individuals and small businesses, the mFax app lets you send a compliant fax from your phone in under 2 minutes — without touching a fax machine. For teams, mFax Business adds virtual fax numbers, HIPAA-ready transmission, team accounts, and full delivery audit logs starting at about $9/mo. Instead of locking you into fixed tiers, you build your own plan — dial in the exact number of seats (1–35) and pages (200–5,000) you need with a live calculator and pay only for what you use.
If you're still working with a physical machine, our guide on how to use a fax machine walks through the complete setup process including Station ID configuration.
Frequently Asked Questions
The FAQ section below is generated from the faqs field in the article frontmatter.