How long do I have to respond to IRS CP105?

Contact the IRS within 10 days if you disagree. Use the deadline printed on your notice and verify how it is calculated. IRS deadlines may run from the notice or mailing date and are not automatically extended because the letter arrived or was opened late.

What should I do if I received IRS CP105?

Compare the notice with your return, then pay by the due date or call or write the IRS within 10 days if you disagree. If you are unsure, have a tax professional review the letter before you respond to the IRS.

IRS CP105 Notice: Miscalculation on Your Return, Balance Due

The IRS found a miscalculation on your return and you now have a balance due. Pay by the due date, or contact the IRS within 10 days if you disagree.

Published by the Law Offices of Darrin T. Mish, P.A.Updated October 13, 2026

Notice: CP105
Urgency: Urgent
Deadline: Contact the IRS within 10 days if you disagree

Your first move

Compare the notice with your return, then pay by the due date or call or write the IRS within 10 days if you disagree.

A CP105 notice means the IRS changed your tax return because it found a miscalculation. As a result, you have a balance due.

This notice is used for returns such as Form 2290 (Heavy Highway Vehicle Use Tax), Form 706 (Estate and Generation-Skipping Transfer Tax), Form 709 (Gift and Generation-Skipping Transfer Tax), Form 730 (Monthly Tax Return for Wagers), and Form 11-C (Occupational Tax and Registration Return for Wagering).

What to Do

Read the notice carefully and compare its figures with your return.
If you agree, correct the copy of the return you kept for your records.
Pay the amount you owe by the payment due date on the notice.
If you disagree, contact the IRS within 10 days of the notice date.

If You Disagree

Call the toll-free number on your notice or write to the address on the contact stub within 10 days of the notice date. The IRS can reverse the change if your response provides additional information that justifies a reversal.

Ten days is short. Pull your return and the supporting figures the day the notice arrives. If you write, keep a copy and use certified mail so you can prove when you responded.

If You Can't Pay

Request a payment plan if you can't pay the full amount.

Interest: None if you pay in full by the payment due date on the notice. After that, interest accrues on the unpaid balance.
Penalty: You'll get a late payment penalty if you can't pay in full. If the reason is circumstances beyond your control, call the toll-free number on your notice by the payment due date. Depending on your situation, the IRS may be able to remove the penalty.

Estates

If the notice relates to an estate return, Publication 559, Survivors, Executors, and Administrators, and Publication 947, Practice Before the IRS and Power of Attorney, cover who can act for the estate and how to authorize a representative.

Next Time

File electronically where you can, and review the return for accuracy before you mail it.

If you received a CP105 notice and need help disputing or paying the balance, call us at (813) 229-7100.

This letter has a clock on it. Don’t run it out alone.

Free consultation with Darrin T. Mish, a Tampa tax attorney licensed since 1993 and admitted to the U.S. Tax Court. Bring the letter.

Call (813) 229-7100

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