IRS notice, decoded
CP161: Unpaid Balance Due (Business Notice)
What it is
A business-account bill: irs.gov files this notice under its Businesses & Self-Employed section, and it plays the role for business tax accounts that the CP14 first bill plays for individuals. The IRS says you received it because you have an unpaid balance due; the notice explains how the IRS calculated the amount and lists the payments applied to your account.
Why you got it
Sent when a tax account has an unpaid balance due.
The deadline structure
The notice prints a pay-by date ('pay the amount due by the date on the notice') — the IRS page publishes no fixed day count for payment. Separately, the page says to contact the IRS within 10 days of the notice date if you think the IRS made a mistake.
The pay-by date printed on YOUR notice controls.
How to respond
- Compare first: the IRS page says to read the notice's calculation, compare its figures with your tax return, and check the list of payments applied to see that every payment you made was credited
- Call the toll-free number on your notice if you disagree — the page says to have documentation (such as cancelled checks or an amended return) ready when you call
- Contact the IRS to make payment arrangements if you can't pay the full amount (the notice page lists Form 9465, Installment Agreement Request)
- Form 2848 (Power of Attorney) if you want an authorized representative to handle it
What ignoring it leads to
The IRS page says interest will continue to increase on the unpaid balance after the payment due date, and that a late payment or failure to deposit penalty will apply. For what follows if the balance stays unpaid, the page's reference list points to Publication 594, The IRS Collection Process.
First: confirm this bill is really from the IRS
- The IRS normally makes first contact by mail delivered by the U.S. Postal Service — and the IRS says a social media direct message is never from the IRS
- IRS-listed scam warning signs: the contact is unexpected, rushes you, threatens you, demands payment now, or asks for personal or financial information — pressure on a business's 'urgent tax debt' is a classic pattern
- To verify, search 'CP161' in the IRS notices and letters pages at irs.gov, or call the phone number on your letter
- Checks, certified funds, or money orders are payable to 'United States Treasury' — and you can pay online at irs.gov
Mistakes people make with a CP161
- Paying without comparing — the page's first steps are to check the notice's calculation against your return and to confirm every payment you made was actually applied to the account
- Sitting on a disagreement — the page says to contact the IRS within 10 days of the notice date if you think a mistake was made, not to wait until the pay-by date
- Ignoring it because the business can't pay in full — the page says to contact the IRS for payment arrangements; interest keeps increasing on the unpaid balance after the due date either way
Official sources
- Understanding your CP161 notice
- Topic no. 653, IRS notices and bills, penalties and interest charges
- How to know it's the IRS
Our summary paraphrases these sources. Last verified: BUILD 2026-07-11 (Claude Fable 5; researched from live irs.gov fetches: https://www.irs.gov/individuals/understanding-your-cp161-notice, https://www.irs.gov/taxtopics/tc653, https://www.irs.gov/newsroom/how-to-know-if-its-really-the-irs) — re-verify before launch. Your printed notice always controls.
NoticeKey is not affiliated with, or endorsed by, the IRS or any state tax agency.
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