How to Fax a Response to IRS Letter 324C (LTR 324C)

What IRS Letter 324C actually means

IRS Letter 324C means the IRS received your amended return but cannot process it yet. Something in the filing is incomplete. Usually that something is an explanation.

Letter 324C is tied to Form 1040-X, the amended individual return. When you change a number on your original return, the IRS wants to know why. Part III of Form 1040-X is where that reasoning belongs. Many filers leave it thin. A single line like "corrected income" gives a reviewer nothing to approve.

This letter is not an audit. It is not a penalty notice either. Nothing on it says the IRS believes you did anything wrong. A reviewer simply stopped work on your file and asked a question. Any refund tied to the amended figures sits still until you answer.

The letter names the tax year and the form in question. It also lists what the reviewer wants from you. Sometimes that is a written statement in your own words. Sometimes it is a document, like a corrected W-2, a 1099, or a receipt. A filing status change may call for a marriage certificate or a court order. Read the request line by line before you gather anything.

Timing matters more than most people expect. An amended return already moves slowly through the system. A 324C pauses it entirely, and the pause lasts until your reply lands in the right unit.

Where to find the LTR 324C fax number

The fax number for LTR 324C is printed on the letter you received. There is no single national 324C fax number to look up.

That answer surprises people who search for one. Here is why it works this way. Amended returns are handled by IRS campuses in different cities. Your letter came from the campus assigned to your return. The reply has to go back to that same unit. A number copied from a message board may route your papers to the wrong building.

Look in three places on the letter.

• The top right block, near the letter number, the date, and your taxpayer ID.
• The paragraph beginning "If you prefer" or "You may fax your response to."
• The final page, above or below the mailing address for the same unit.

The number usually appears as a standard ten digit US number. Some letters list an 855 or 877 line, others list a direct campus line. Copy it exactly. Digit by digit.

If your letter is damaged or a page is missing, call the phone number on the notice first. The IRS also lists general contact routes on irs.gov. Do not guess a number. A response faxed to an unrelated IRS unit is treated as never received, and your deadline keeps running.

Write the number on your cover sheet as well as in your fax app. That gives you a paper record of where the packet went. It matters later if you ever have to prove you responded on time.

What to include in your 324C response

Your response needs a copy of the 324C letter plus a written explanation for every figure you changed. Supporting documents come after that.

Put the letter on top of the stack. Reviewers work from it, and a packet with no letter attached can sit unmatched for weeks. If the letter carries a barcode or a tear-off stub, keep it flat and intact.

Next comes the explanation. Write it as a short numbered statement with one item per change. For each item, name the line on Form 1040-X. State the old figure and the new figure. Then say in plain words what caused the difference.

Here is the level of detail that works: "Line 1, income reduced from $61,400 to $58,900. Employer issued a corrected W-2c in March after a payroll error." A reviewer can approve that without calling you.

Then attach your proof. A corrected W-2 or 1099. A closing statement. A tuition form. A court order for a dependency change. Send only what supports a figure you actually altered. Extra paper slows the review and can raise questions nobody asked.

Add a cover sheet at the front. It should carry your name, your taxpayer identification number in the format the letter uses, and the tax year. Add the letter number and a total page count too. Page counts matter because fax transmissions can drop a sheet, and the reviewer needs a way to notice.

Keep every original. You are sending copies only. Never fax an original document you cannot replace, since IRS correspondence units do not mail paperwork back.

How to fax your 324C response step by step

Fax your 324C response by stacking the pages in order and sending them to the number printed on your letter. The task takes a few minutes.

You do not need a fax machine for this. Faxing today runs over internet protocols such as T.38, which carry the same signal a physical machine would send. The receiving IRS unit sees an ordinary fax either way.

Faxend handles all of this from a phone or a browser. You can send from the web at faxend.com/send or from the iPhone app. The first send costs $2.99 and needs no account or subscription. Pages are encrypted with AES-256 in transit and at rest. For a walkthrough with screenshots, read our guide on how to send a fax from iPhone.

Your deadline, and what happens after you send

Your response deadline is printed on the letter itself. IRS correspondence letters commonly allow 20 or 30 days from the letter date. Count from the date on the page, not the day it reached your mailbox.

Mail delays eat into that window. This is the main practical reason filers fax a 324C instead of mailing it. A fax arrives the same day and produces a timestamped confirmation you control. A mailed reply spends days in transit, and certified mail proves delivery to a mailroom rather than to the reviewing unit.

Once your fax goes through, the file returns to the amended return queue. Processing is not instant. The IRS asks filers to allow roughly 16 weeks for an amended return in normal conditions. A file that was paused can run longer than that. Check progress through Where's My Amended Return instead of calling during the first few weeks.

If you cannot meet the deadline, call the number on the letter before it passes. Ask for additional time and write down who you spoke with. Missing the date without contacting anyone can lead the IRS to disallow the changes on your 1040-X. Reversing that later is a slower fight than answering on time.

If months pass with no movement and you are facing real hardship, help exists. The Taxpayer Advocate Service is an independent office inside the IRS that takes these cases.

Mistakes that restart the clock

The most common 324C mistake is sending documents with no written explanation attached. Paper alone rarely answers the reviewer's actual question.

A close second is the opposite error. Some filers send a long explanation and no proof behind it. The reviewer needs both halves. Treat the statement as your argument and the documents as your evidence.

Other problems show up again and again in these responses.

• No page numbers. If a sheet drops during transmission, nobody can tell it is missing.
• Faded copies. A phone photo shot in shadow can swallow the decimal point in a dollar figure.
• Mixed tax years. If you amended two years, send each response as its own fax with its own cover sheet.
• Staples and folds. Flatten everything first, because staple shadows show up as black bars.
• No confirmation saved. Without it you have no proof of your send date.

One habit prevents most of these. Before sending, read your own packet as though you were a reviewer who has never seen your file. If any part needs you standing there to explain it, rewrite that part. Our editor Faxley covers this pattern across the IRS fax guides on this site.

Fax or mail: which to use for a 324C

Fax is the faster option for a 324C response, and it gives you a same day timestamp. Mail is the fallback when your packet is very large or your letter lists no fax number.

Use both when the stakes are high and the deadline is close. Fax first, so the timestamp lands inside the window. Then drop a paper copy in certified mail the same day. Note on the mailed cover sheet that a fax already went out, with its date and time.

If your response runs past roughly 25 pages, split it. Send two faxes and label the cover sheets 1 of 2 and 2 of 2. Repeat your identifying information on both. Long single transmissions are more likely to drop a page somewhere.

Cost deserves a line too. Faxend charges $2.99 for a one time send of up to five pages, with no account required. The $9.99 monthly Standard plan covers 20 pages and keeps a saved history. Full details sit on the pricing page. If you expect to answer several IRS letters this year, a plan with history is easier to defend later. Worth comparing against our roundup of the best fax apps for iPhone and the case for faxing without a subscription.

Frequently asked questions

What is the fax number for IRS Letter 324C?

The fax number is printed on your 324C letter, usually in the response instructions near the top or on the last page. The IRS does not publish one national number for this letter, because it routes back to the campus that issued it.

Can I fax my IRS Letter 324C response from my phone?

Faxend lets you fax a 324C response from your iPhone in about a minute, and the first send is $2.99 with no subscription. Scan or photograph each page, enter the number printed on your letter, then save the confirmation.

Is Letter 324C an audit?

No. Letter 324C is a request for information about your amended return, not an examination. The IRS cannot finish processing Form 1040-X without an explanation of the changes you made.

How long do I have to respond to LTR 324C?

The deadline is printed on your letter. IRS correspondence letters commonly allow 20 or 30 days from the letter date. Call the number on the notice if you need more time.

What happens if I ignore Letter 324C?

The IRS can disallow the changes on your amended return and close the file. Any refund tied to those changes would not be issued. Reopening the matter later takes far longer than answering the letter.

Should I fax or mail my 324C response?

Fax is faster and gives you a same day confirmation with a page count. Mail works better when your packet is very large or your letter lists no fax number.