CP161

A CP161 tells a business it has an unpaid balance — the business-side counterpart of a first bill. It shows how the IRS calculated the amount and which payments it applied.

“Here is the balance we calculated, and here is the list of payments we applied. Compare it to your return — if you think we made a mistake, contact us within 10 days. Otherwise, pay by the date on the notice or arrange payments.”

The IRS's page asks businesses that see a mistake to make contact within 10 days of the notice date — a short window, and the most common reason to act quickly on this one. Payment itself is due by the date printed on the notice.

• The notice, especially the payment-application list
• The business return for the year shown
• Deposit and payment records — misapplied deposits are a frequent cause of these bills
• Prior-year notices if the balance carried over

• Reconciling the IRS's payment list against the business's actual deposits
• Contacting the IRS inside the 10-day window when the bill looks wrong
• Arranging payment plans or an offer in compromise when the balance is real
• Authorized representation (Form 2848) so the IRS deals with your representative directly