What CP 161 is
"A CP 161, No Math Error, Balance Due, is issued to taxpayer as a first notice to notify them of tax, penalties, or interest due on any BMF return with a balance due of $1.00 or more and no math errors" (IRM 21.3.1.7.19, Apr. 23, 2024). The return itself was accepted as filed; the balance "may result from a missing payment or the assessment of penalties such as failure to file (FTF), estimated tax (ES), or dishonored check penalties." On a Form 945 the usual cause is a deposit that posted to the 941 module or to the wrong year, or a deposit penalty on a late deposit. The assistor's script for a caller who says a payment is missing is "Research for payment. Refer to IRM 21.5.7, Payment Tracers."
The deadline
Pay by the date on the notice to avoid further interest and the failure-to-pay penalty; the notice-and-demand window is 21 calendar days (10 business days at $100,000 or more). Unanswered, the module moves to the reminder notices and then CP504.
What to do
Compare the deposits credited on the notice to your EFTPS history for the Form 945 tax type and year. If a deposit is missing, call with the EFTPS acknowledgment number, amount and date and ask for a credit transfer to the 945 module with the original payment date; the misapplied-deposit page covers what the assistor needs. If the balance is a deposit penalty, the Form 945 deposit penalty calculator and the first-time abatement rules apply. If the balance is correct, pay it or set up the payment plan the CP504 page describes before the notice sequence advances.
Questions about CP 161
Who receives CP 161?
Any business filer, including a payer whose Form 945 posted with less credit than it claimed. "A CP 161, No Math Error, Balance Due, is issued to taxpayer as a first notice to notify them of tax, penalties, or interest due on any BMF return with a balance due of $1.00 or more and no math errors" (IRM…
What is the deadline on CP 161?
Pay by the date on the notice to avoid further interest and the failure-to-pay penalty; the notice-and-demand window is 21 calendar days (10 business days at $100,000 or more). Unanswered, the module moves to the reminder notices and then CP504.
What should I do when CP 161 arrives?
Compare the deposits credited on the notice to your EFTPS history for the Form 945 tax type and year. If a deposit is missing, call with the EFTPS acknowledgment number, amount and date and ask for a credit transfer to the 945 module with the original payment date; the misapplied-deposit page covers what the assistor needs. If the balance is a deposit penalty, the Form 945 deposit penalty calculator and the first-time abatement rules apply. If the balance is correct, pay it or set up the payment plan the CP504 page describes before the notice sequence advances.
Is CP 161 about my own income tax?
No. This decoder covers information reporting and withholding: the notices a payer, filer or payee sees because of Forms 1099, W-2, 945 and the TINs on them. Individual income-tax notices follow a different track.
Have a different notice? The IRS notice decoder lists all 89 in the order they tend to arrive.