CP105 Notice: The IRS Found a Miscalculation on Your Estate, Gift or Excise Return

What a CP105 says

The IRS CP105 page says, “We made changes to your tax return because we found a miscalculation. As a result of these changes, you have a balance due.”

The notice covers a small group of returns. IRM 3.14.2 Exhibit 3.14.2-10 pairs the CP105 with Forms 11-C, 2290, 706, 706-NA, 709, 709-NA and 730: wagering, heavy highway vehicle, estate and gift returns. If you run a trucking business, the page also points to its Trucking Tax Center. If you handle an estate, it points to Publication 559.

IRM 3.14.2.6.7.1.5 tells staff to review these estate and gift returns “per normal math error procedures.” That matches what the page describes: the IRS recomputed the return and changed the numbers.

The 10-day window

The most important line on the IRS page sits in its list of steps: “Contact us within 10 days of the date of your notice if you disagree with the changes we made.” The clock runs from the notice date, not from the day you open the envelope.

You have two ways to do it. The page says you can “call us at the toll-free number on your notice or write to us at the address on the contact stub.” Whichever you choose, keep a record of the date.

Your reply needs substance. The page says, “We can reverse the change to your account if your response provides additional information that justifies a reversal.” Send the additional information that supports your figure.

If you agree with the change

Correct the copy of the return you kept, then pay the balance by the payment due date on the notice. The page says, “We don’t charge interest if you pay the full amount you owe by the payment due date on the notice.” After that date, interest accrues on the unpaid balance.

If you can’t pay in full, request a payment plan. You should still expect a late payment penalty. The page answers plainly: “Yes, you will receive a late payment penalty.”

That penalty may not stick. If you can’t pay because of circumstances beyond your control, contact the IRS by the due date of your payment. The page says “we may be able to remove the penalty” depending on your situation.

What people mistake a CP105 for

Many people read it as a routine bill and pay it. Check it first. The notice shows the IRS’s math, and you can compare each figure with the return.

Others assume they can wait for a final notice before they respond. The IRS page names 10 days, so reply by then. If you miss that date on an estate or gift return, IRC 6213(b)(2)(A) may still let you ask the IRS to abate, or cancel, the assessment “within 60 days” after the notice.

Business owners often confuse it with a CP102, which covers employment tax returns, or with a CP161, which reports a balance due with no math error. The return on your notice tells you which one you have.

For tax professionals

The 10-day line needs care on estate and gift returns. IRC 6213(b)(2)(A) lets a taxpayer ask for abatement of a math error assessment “within 60 days” after the notice, and Treas. Reg. 301.6213-1(b) says a math error notice is not a notice of deficiency. That section sits in the deficiency rules, which reach estate and gift taxes. They do not reach the excise taxes on Forms 2290, 730 and 11-C.

The CP105 page does not mention the 60-day rule. Do not read that silence as a waiver. Reply within 10 days. Then weigh the abatement request: IRC 6213(b)(2)(A) says that on a timely request “the Secretary shall abate the assessment,” and any reassessment “shall be subject to the deficiency procedures.” IRC 6213(b)(2)(B) bars levy during that period.

A change is coming. Pub. L. 119-39 section 2 requires a math error notice to “display the date by which the taxpayer may request to abate,” for notices sent after “the date which is 12 months after Nov. 25, 2025.” Check a new CP105 for that date. Our math error abatement clock counts the same period, but it lists only individual notices, so count that period from the notice date yourself.

For Forms 706 and 709, IRM 3.14.2.6.7.1.5 says Notice Review cannot adjust the account and must route the return to Cincinnati SB/SE. That section covers Notice Review’s own work, not your reply. If you sign for the client, the page points to Publication 947 on practice before the IRS and power of attorney.

Common Questions