IRS Form 433-D Fax Number: Fax vs. Mail and What to Check

There is no universal IRS Form 433-D fax number. The right number depends on which IRS office or Collection Field function is handling your installment agreement, and it appears on the letter the IRS sent with your copy of the form. If that letter is gone, call the phone number on your most recent IRS notice and ask for the fax number that goes with your case.

Where to Find the Right Fax Number

The IRS assigns installment agreement cases to specific service centers and field offices around the country, and each office has its own fax line. The form itself tells you to “return Part 1 to IRS at the address on the letter that came with it or the address shown in the ‘For assistance’ box on the front of the form.”¹ The same principle applies to faxing: the number belongs to the office holding your case, not to the IRS at large.

Check these sources in order:

The cover letter that came with your Form 433-D. It lists the contact information for the office responsible for your account.
The “For assistance” box on the front of the form. Some versions include an office contact there.
Your most recent IRS notice about the underlying tax debt. Call the phone number printed on it and ask for the fax number for submitting a signed 433-D.
As a last resort, the IRS general line at 800-829-1040. Expect long hold times, and have your Social Security number and notice ready.

Faxing the form to the wrong office is one of the more common mistakes taxpayers make with Form 433-D. It doesn’t just slow the paperwork; it can leave you exposed to continued collection activity while an office that isn’t yours ignores a document it has no reason to act on.

Faxing vs. Mailing

Faxing is faster, but the confirmation you get is that a fax machine picked up, not that the right unit received your form. Keep the fax confirmation page showing the date, time, and number you dialed. A week or two later, call the office and confirm your signed 433-D is in the file.

Mailing is slower but leaves a stronger paper trail. Send the form to the address on the cover letter or in the “For assistance” box, and use certified mail with return receipt requested. If the IRS later claims your form arrived late or not at all, the green card is the answer.

What to Check Before You Send It

Form 433-D may arrive partially filled in by an IRS employee or blank for you to complete.¹ Either way, read every field before signing. The ones that matter most:

Your Social Security number or EIN. A wrong taxpayer identification number can send payments to the wrong account and take months to fix.
The monthly payment amount. It should match what you agreed to over the phone or with the revenue officer.
The day of the month payments are due.
The kinds of taxes, tax periods, and total liability listed. Make sure they match your understanding of what the agreement covers.

If a joint liability with a spouse is involved, both signatures are required. An unsigned form will not be processed, which means further delay and, potentially, further collection activity in the meantime.¹ If any term looks wrong, contact the office handling your case before you sign. Don’t sign a form with incorrect terms and plan to fix it later.

If you’re authorizing direct debit, the form has a section for your bank’s routing number and account number, and the account must be at a U.S.-based financial institution. Confirm both numbers against a check or a bank statement. If you later need to stop a scheduled withdrawal, the form directs you to notify your financial institution at least three business days ahead, or the IRS at least 14 business days ahead.¹

After You Send the Form

Start making payments on the schedule you agreed to as soon as you sign, without waiting for an acceptance letter. The terms bind you from the moment you sign the form, and the IRS will send a confirmation letter once the agreement is officially in effect.

Keep three documents together in one place: your signed copy of Form 433-D, the fax confirmation page or the certified mail receipt, and the eventual acceptance letter. If a payment issue comes up later, or if you ever need to prove the agreement was active during a particular period, that packet is your evidence.

One Thing Form 433-D Is Not

Form 433-D is not how you ask the IRS for an installment agreement. It’s the written confirmation of an agreement the IRS has already agreed to: the monthly amount, the due date, the tax periods, and the total liability.¹ The request form is Form 9465.² Some situations also require Form 433-A (individuals) or Form 433-B (businesses) so the IRS can evaluate your finances before agreeing to terms.

If you owe $50,000 or less and qualify for a streamlined agreement, you may be able to set the whole thing up through the IRS Online Payment Agreement tool without ever seeing a 433-D.³ The form shows up most often when the arrangement was worked out with a revenue officer or over the phone, and it’s returned to the office that negotiated it. That’s why the fax number is on the letter, not printed on the form.

1
Internal Revenue Service. Installment Agreement Form 433-D
2
Internal Revenue Service. About Form 9465, Installment Agreement Request
3
Internal Revenue Service. Online Payment Agreement Application