Mistake, Bad Advice, "I Did Not Know," "I Forgot": Reasons the IRS Tests Hard

By Forrest Baumhover, CFP®, EA · Last verified October 30, 2026

Forgetting, a mistake or relying on a preparer rarely works alone. Here is what each one needs, and where the facts can favor you.

Why These Reasons Start Behind

Each reason here points at something you could have controlled, so it runs into the reasonable cause test head on. The IRM says a mistake or forgetfulness alone generally does not provide a basis for reasonable cause (IRM 20.1.1.3.2.2.4, IRM 20.1.1.3.2.2.7).

The rule to remember: you can hire help, but you cannot hand off the deadline. The IRM says your responsibility to file and pay "cannot be delegated" (IRM 20.1.1.3.2.2.7). Each reason can still work when other facts show you used ordinary care.

What people mistake an honest error for

People think honesty is the test. The IRS can believe you and still deny relief, because the question is whether you used care, not whether you meant well. The reason for the mistake can support a request, but it needs other facts beside it (IRM 20.1.1.3.2.2.4).

When You Made a Mistake

The IRM looks at when and how you learned of the mistake, how far you corrected it, and whether you acted in time once you found it (IRM 20.1.1.3.2.2.4). If you gave the task to a subordinate, it also looks at your relationship with that person. Bring your supporting documents.

Bad Advice or Relying on Someone Else

The IRS first sorts your claim into one of two kinds (IRM 20.1.1.3.2.2.5). Did someone give you specific advice that you followed, or did you count on someone to do the job for you? The answer changes the result.

Counting on someone to file or pay is the weak claim. In United States v. Boyle, an executor relied on an attorney who missed a filing date, and the Supreme Court held that reliance was not reasonable cause: "one does not have to be a tax expert to know that tax returns have fixed filing dates" (469 U.S. 241, 251). IRS.gov adds that you should get proof your return or payment went in on time.

Following advice on the law is the stronger claim. Boyle separates the two: when a professional advises you on a matter of tax law, such as whether a liability exists, it is reasonable to rely on that advice (469 U.S. at 251). Even so, the IRM says this works outside the accuracy penalty only "in very limited instances," on technical or complicated issues (IRM 20.1.1.3.3.4.3).

Advice from the IRS has its own rules. The law generally requires the IRS to remove a penalty caused by erroneous written advice from an IRS employee (IRC §6404(f); IRM 20.1.1.3.3.4.1). For phone or in-person advice, keep your question, the answer, the date, the office and the employee's name (IRM 20.1.1.3.3.4.2).

Reliance can also work in a narrower way. The IRM asks whether you lost access to your own records, or whether a tax law change caught you that you could not reasonably know about (IRM 20.1.1.3.2.2.5).

I Did Not Know the Rule

The test requires "reasonable efforts" to learn your tax duties, and the IRM says reasonable cause "should never be presumed" (IRM 20.1.1.3.2.2.6). Ignorance works only with other facts. The IRM names your education, whether you owed this tax before, any prior penalty, recent changes in forms or law, and how complex the issue is.

The IRM says you may have reasonable cause in two cases. You made a reasonable and good faith effort to comply, or you did not know of the rule and had no reasonable way to know of it.

I Forgot

This is the weakest reason here, whether you forgot or someone else did. The IRM says it generally does not provide a basis for reasonable cause, and that relying on another person is generally not enough (IRM 20.1.1.3.2.2.7). If forgetting is your only reason, look at other relief paths first.

The Exception: A Notice You Could Not Read

This reason runs the other way, because it starts from something outside your control. If a disability kept you from reading a standard print notice, you can ask for penalty relief, but you must still meet the reasonable cause standard (IRM 20.1.1.3.2.2.8).

The IRM asks you to describe the impairment, say when you got the notice and when you learned of the issue, and say what you already knew about the amount owed. It also asks when the IRS learned you need accessible notices, and whether you responded promptly once you got one.

What you already knew can sink the request. In the IRM's CP14 example, a taxpayer filed a return showing tax due and paid nothing, so that person knew of the debt before the notice and would not qualify.

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