855-279-2109 is an IRS fax number, not a phone line. It’s printed on Notice CP63, the letter that says the IRS is holding your refund because it hasn’t received one or more of your past tax returns. The CP63s we’ve seen don’t list a phone number at all, which is why so many people end up searching this one.
Updated September 25, 2026 · Checked against real notices our clients received
IRS fax number lookup
855-279-2109
IRS fax line, not a phone line
- What it is
- An IRS fax number listed on Notice CP63.
- Printed on
- Notice CP63, “We’re holding your [year] tax refund.”
- What to fax
- Your signed and dated missing returns, or a written explanation of why you didn’t have to file, with a copy of the notice.
- Deadline
- The date on your notice. The CP63 we reviewed gave 10 days.
- Mail instead
- Internal Revenue Service, Stop 5501, P.O. Box 149338, Austin, TX 78714-9338, as printed on the notice we reviewed. Use the address on yours.
- To talk to someone
- The IRS’s main line for individuals is 800-829-1040, 7 a.m. to 7 p.m. local time on weekdays.
Why the IRS sent you a CP63
You filed a recent return that shows a refund. But IRS records show that one or more earlier returns are missing, and the IRS thinks you’ll owe tax for those years. So it’s holding your refund until it hears from you.
The CP63 we reviewed, dated May 19, 2025, is a typical example. It told the taxpayer the IRS was holding their 2024 refund because the 2020 through 2023 returns hadn’t been filed, and it asked for those returns by May 29, 2025.
Once the IRS gets the returns or an explanation, it figures out whether you owe. If you do, it applies some or all of the refund to the balance, then sends a notice explaining how it used the money and a check for anything left over.
If you don’t respond, the notice says the IRS will keep holding the refund and may determine your tax based on third-party information, like the W-2s and 1099s employers and banks sent in.
Your three ways to respond
| Option | When it makes sense |
|---|---|
| E-file through a tax preparer | The notice calls this “the best option if you can file the missing return within 2 years from the year it was originally due.” |
| Fax to 855-279-2109 | Fast, and you get a transmission receipt. Send signed and dated returns with all supporting forms and schedules. |
| Use the address printed on your notice, and send it with tracking. |
How to fax the IRS without problems
- Put a copy of the CP63 on top. The notice asks for it with any explanation, and it helps the IRS match your pages to your account.
- Sign and date every return. The notice specifically asks for signed and dated returns.
- Include every supporting form and schedule that belongs with each return.
- Use a regular fax machine or an online fax service. The notice allows either one. Pick a service you trust, since you’re sending full tax returns.
- Save the confirmation page showing every page went through, and keep a complete copy of what you sent.
Two traps to avoid
- Waiting on years that have refunds of their own. You generally have three years from a return’s due date to claim a refund on it. If any of your missing years would produce a refund, that clock is running.
- Letting the IRS figure your tax for you. When the IRS works from third-party records, it doesn’t know about deductions and credits you’d claim yourself, so the bill is usually higher than it should be.
Who to call about a CP63
The IRS page for Notice CP63 tells you to call the toll-free number on your notice. The CP63s we’ve reviewed don’t print one. Your options:
- Call the IRS’s main line for individuals at 800-829-1040 (7 a.m. to 7 p.m. local time, weekdays). The IRS says waits are longest on Mondays and Tuesdays.
- Check which years the IRS shows as unfiled in your online account at IRS.gov/account.
- Have a tax professional handle it. With a power of attorney, we can pull your IRS wage and income records, prepare the missing returns and send them in.
Behind on filing?
We’ll prepare the missing returns and deal with the IRS
Our CPAs pull your IRS income records, prepare every missing year, and send the returns in the right way. If you end up owing, we’ll set up the resolution too. Learn more about our unfiled tax return service.
855-279-2109 FAQs
Can I call 855-279-2109?
No. The CP63 lists 855-279-2109 as a fax number for sending returns and documents, so calling it won't get you a person. For questions, the IRS's main line for individuals is 800-829-1040.
What should I fax to 855-279-2109?
Your signed and dated missing tax returns with all supporting forms and schedules, or a written explanation of why you didn't have to file, along with a copy of the CP63.
How long will the IRS hold my refund?
Until you file the missing returns or explain why you didn't have to. The IRS then processes the returns, applies the refund to any balance you owe, and sends a check for whatever is left.
What if I already filed those returns?
Tell the IRS. Its CP63 page says you can explain that you've already filed. Send a signed copy of each return with a copy of the notice by fax or mail, and keep proof of what you sent.
Can I use an online fax service to send my returns?
Yes. The CP63 we reviewed says you can fax using a traditional fax machine or an online fax service. Choose a reputable service, because you'll be sending your full tax returns.
What happens if I ignore a CP63?
The IRS keeps holding your refund and may determine your tax for the missing years using third-party information. That usually produces a higher bill than filing yourself.
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Other numbers from IRS and state tax notices
Sources
- Redacted Notice CP63 received by one of our clients (PDF), dated May 19, 2025.
- IRS, Understanding your CP63 notice.
- IRS, Telephone assistance.
Choice Tax Relief is a private tax resolution firm. We are not the IRS, the U.S. Treasury, or any government agency, and we are not affiliated with any private collection agency. You can call the IRS yourself at no charge. This page is general information, not legal or tax advice for your situation.