A CP161 is an IRS bill. It says you have an unpaid balance on a tax account and explains how the IRS figured the amount. IRS reference material describes it as a notice of tax, penalty and interest due on a return without a math error. It's used for business-type accounts rather than individual Form 1040 accounts, which get a CP14. A CP161 is not an audit and not a final notice. But businesses can build up penalties quickly, especially on payroll taxes, so it pays to act within days.
Why you got a CP161
IRS Document 6209, an internal reference guide, lists the CP161 among business notices. It's used for returns without a math error, except partnership returns (Form 1065). The IRS's CP161 page points readers to guides for employers (Publication 15), corporations (Publication 542), estates and survivors (Publication 559) and exempt organizations with unrelated business income (Publication 598). That gives a sense of who receives it. Common causes:
- The return showed a balance that wasn't fully paid. For example, a Form 941 payroll return or a corporate return filed without full payment.
- Deposits were late, short or missing. Employers who don't make required federal tax deposits on time can owe a failure-to-deposit penalty.
- A payment was misapplied. It went to the wrong period, form or EIN.
- Penalties and interest. The tax may be paid, but penalties and interest charged on late payment remain.
What the CP161 says
The IRS says to read the notice carefully, because it explains how the amount due was calculated. Look for:
- The amount due, split into tax, penalties and interest.
- The tax form and period, such as a specific quarter for Form 941.
- The list of payments and deposits the IRS applied. Check it against your bank records and EFTPS history.
- The payment due date.
- Contact information and a payment stub.
What to do
- Compare the notice with your return. Make sure the tax figures match what you filed.
- Check every payment. The IRS says to check the list of payments it applied to see whether all of yours were included. Look for deposits made under the wrong period or EIN.
- If you think the IRS made a mistake, contact it within 10 days of the notice date. Call the toll-free number on the notice with documentation, such as canceled checks, EFTPS confirmations or an amended return.
- If you agree, pay by the due date. The IRS says it won't charge additional interest if you pay the full amount by then. Businesses can pay through EFTPS (free, enrollment required), Direct Pay or other options at IRS.gov/payments.
- If you can't pay in full, call to set up a payment arrangement. Business taxpayers should call the number on the notice or 800-829-4933. Publication 594 says a business that owes $25,000 or less in assessed payroll taxes, penalties and interest for the current and prior calendar year can also use the Online Payment Agreement application. Sole proprietors and independent contractors apply as individuals.
- Consider a representative. You can authorize an accountant, enrolled agent or attorney to deal with the IRS for you by filing Form 2848.
For an approved long-term plan, the IRS lists 2026 setup fees of $29 online or $107 by phone, mail or in person with direct debit, and $69 online or $178 by phone, mail or in person for other payment methods. Short-term plans of 180 days or less have no setup fee, though the IRS says only individuals can apply for those online. See IRS payment plans. An optional installment agreement kit is available on this site if you want help preparing a request.
If paying the full amount isn't realistic, the IRS also points to an offer in compromise. For more on running a business through an IRS balance, see our small business owners hub.
What happens if you ignore it
- Penalties grow. The IRS says you'll owe a late payment or failure-to-deposit penalty, depending on what you owe. The general failure-to-pay penalty is 0.5% of unpaid tax per month, up to 25%.
- Interest keeps accruing after the due date. The IRS underpayment rate was 7% for most of 2026 (6% in April–June) and is set quarterly.
- Collection escalates. Further notices can include a lien filing (Letter 3172) and a final notice of intent to levy, such as a CP297 for business accounts in the federal payment levy program (see CP90/CP297) or an LT11/Letter 1058. A revenue officer may be assigned.
- Owners can become personally liable for payroll taxes. For unpaid employment taxes, Publication 594 explains the Trust Fund Recovery Penalty. It's assessed personally against the people who were responsible for paying the withheld "trust fund" taxes but willfully didn't, and it equals the unpaid trust fund taxes.
Is this notice real?
Verify a CP161 by calling the IRS business line, 800-829-4933, or the number for your notice listed on IRS.gov. Compare the EIN and tax period with your records. Pay only through EFTPS, IRS.gov/payments, or a check to the "United States Treasury." The IRS doesn't take payment by gift card or wire to an individual. See IRS scams.
Frequently asked questions
Is a CP161 only for businesses?
It's mainly used for business-type accounts, such as employment tax, corporate, estate and exempt organization returns. Individuals with a balance on Form 1040 normally get a CP14 instead.
What's the 10-day deadline about?
The IRS asks you to contact it within 10 days of the notice date if you think it made a mistake. That's separate from the payment due date. If you agree with the bill, just pay by the due date.
Will I be charged more interest if I pay by the due date?
No. The IRS says it doesn't charge additional interest if you pay the full amount by the payment due date. Interest continues on any unpaid balance after that date.
Can the penalties be removed?
Possibly, if you had reasonable cause or qualify for other relief. Notice 746 explains penalties and interest, and our IRS penalty relief guide covers how to ask.
Sources
- Internal Revenue Service (IRS), "Understanding your CP161 notice". irs.gov
- IRS, Document 6209, Section 9: Notices and Notice Codes (2018). irs.gov
- IRS, Publication 594, The IRS Collection Process (Rev. 1-2026). irs.gov
- IRS, "Payment plans; installment agreements". irs.gov
- IRS, "Failure to pay penalty". irs.gov
- IRS, "Quarterly interest rates". irs.gov
IRSV.com is an independent guide and is not affiliated with the IRS. This page is general information, not tax or legal advice. Rules change; confirm details on IRS.gov or with a tax professional. Found an error? Tell us.