Fax Troubleshooting: Why Your Fax Failed and How to Fix It (2026)

If your fax failed, don’t panic. Most issues come down to number formatting, destination device status, or document quality. Here’s a quick, practical checklist.

Quick Fix Checklist (2 Minutes)

Re-enter the number in international format (e.g., +1 212 555 0123)
Remove leading zeros from international area codes
Resave as PDF and ensure black text on white
Try during recipient business hours
Send a 1‑page test first

See basics: How to Send a Fax Online

Common Error Causes

Busy destination line: Try again or call ahead
Invalid number format: Use +[country] [area] [local]
Poor quality scans: Rescan at 300 DPI, high contrast
Large files: Compress PDF below 10–15 MB
Recipient issues: Out of paper, unplugged, or off-hours auto-shutdown

International Gotchas

Always begin with ‘+’ and the country code
Drop leading ‘0’ from area codes (e.g., UK 020 → +44 20)
Verify country code here: Country Codes List

When to Switch Methods

Court deadlines today? Fax and send certified mail as backup
Medical emergencies? Fax and call to confirm receipt
Repeated failures? Try a different destination number or contact support

Keep Proof

Save your delivery confirmation email or PDF receipt. It’s your evidence for courts, insurers, and business records.

Retry your fax

Frequently Asked Questions

Why does my fax keep failing?

The most common causes are a wrong number format, a busy destination line, poor connectivity, or an unreadable/oversized file.

How should I format a US fax number?

Use the full 10-digit number with area code. If the service supports it, international format is also fine: +1 followed by the number.

How do I format an international fax number?

Use + plus the country code, then the number. Many countries drop a leading 0 from the area code when using the country code.

What file type works best for faxing?

PDF is usually the most reliable. If you’re using photos, convert them into a single PDF to keep pages in order.