The Six-Year Rule: When Omitted Income Doubles the IRS Assessment Window

Three years is the normal window for the IRS to assess more tax. Leave enough income off the return and the window doubles. Section 6501(e) of the Internal Revenue Code gives the IRS six years when a return omits income above a set threshold, and it does not require fraud, bad intent or even carelessness. A big enough mistake is enough.

This is the rule I see misunderstood more than any other assessment exception. People hear six years and assume it applies to everyone, or they assume it only applies to cheaters. Neither is right. It is a math test with specific inputs, and the inputs are where the arguments live.

The statutory test

Section 6501(e)(1)(A) says that for income taxes, if the taxpayer omits from gross income an amount properly includible and that amount is in excess of 25 percent of the amount of gross income stated in the return, the tax may be assessed at any time within 6 years after the return was filed.

Read that carefully. The comparison is omitted gross income against gross income stated in the return. It is not tax against tax, and it is not net income against net income. Deductions do not enter into it.

There is a second, separate trigger in the same subparagraph. If the omitted amount is attributable to foreign financial assets that must be reported under IRC 6038D (the Form 8938 rules, applied as if there were no dollar threshold) and the omitted amount is more than $5,000, the six-year period applies even if the 25 percent test is not met. That trigger gets more attention in the guide on foreign information returns.

What gross income means for a business

For a trade or business, section 6501(e)(1)(B)(i) defines gross income for this test as the total amounts received or accrued from the sale of goods or services, before reduction for the cost of those sales or services. In plain English, the comparison uses gross receipts, not gross profit.

That definition helps business owners. A retailer with $1,000,000 in sales and $800,000 in cost of goods sold has $200,000 of gross profit, but for the six-year test the base is the full $1,000,000 of receipts. The omission has to exceed a quarter of the larger number before the longer period applies.

Overstated basis now counts as an omission

For years there was a fight over whether overstating the basis of property you sold was an omission from gross income. If you report a sale but claim too much basis, the gain on the return is understated, but nothing was technically left off.

Congress answered that question in the statute. Section 6501(e)(1)(B)(ii) now says an understatement of gross income by reason of an overstatement of unrecovered cost or other basis is an omission from gross income. If inflated basis knocks enough gain off the return, it counts toward the 25 percent test the same way unreported wages would.

That matters for real estate sales, business sales and investment accounts where basis records are thin. The person who reconstructs basis generously is taking a six-year risk, not a three-year one.

Disclosure takes items out of the calculation

This is the most useful part of the statute for taxpayers, and it is underused. Section 6501(e)(1)(B)(iii) says that in determining the amount omitted (other than basis overstatements), an amount is not counted if it is disclosed in the return, or in a statement attached to the return, in a manner adequate to apprise the Secretary of the nature and amount of the item.

The idea is simple. The longer period exists because the IRS cannot audit what it cannot see. If the return itself tells the IRS about the item and its amount, the IRS is not at a disadvantage, and the item does not push you over 25 percent even if you treated it as non-taxable.

The practical lesson: when you take a position that a receipt is not taxable, say so on the return. A clear statement attached to the return can keep a disputed item inside the three-year world. Note the statutory carve-out, though. The disclosure exception in clause (iii) does not apply to the basis-overstatement rule.

Six years is still a limit

The six-year rule is an extension, not an open door. The IRS still has to assess within six years after the return was filed. The same filing rules apply as under the three-year statute: early returns are treated as filed on the due date, late returns start the clock when filed. The three-year guide covers those details.

And six years does not require bad intent. That distinguishes it from the fraud exception, where the IRS can assess at any time but must prove fraud. Under section 6501(e), an honest mistake that is large enough triggers the longer period. Under section 6501(c)(1), fraud removes the limit altogether.

Once the six-year period applies, it applies to the tax for the year, not only to the omitted item. The statute says the tax may be assessed within six years. If the IRS is properly inside the extended period, it can adjust other items on the return too.

Estate, gift and excise returns

The 25 percent concept is not limited to income tax. Section 6501(e)(2) applies a six-year period to estate and gift tax returns that omit items exceeding 25 percent of the gross estate or total gifts stated on the return, with a similar adequate-disclosure exception. Section 6501(e)(3) does the same for certain excise taxes where the omitted tax exceeds 25 percent of the tax reported.

The structure is the same in each: compare what was left off to what was reported, and exclude what was adequately disclosed.

Who has to prove it

When the IRS issues a notice after three years and relies on the six-year rule, the IRS is asserting an exception to the normal period. In practice that means the IRS needs to show the omission and the numbers that put it over the threshold. Your job is to test the math: what was the gross income stated on the return, what exactly was omitted, and what was disclosed.

Many six-year cases turn on a recalculation. Gross receipts get added back in for a business. A disclosed item gets removed from the omission side. A receipt the IRS treats as income turns out to be a loan or a return of capital. Move the numbers and the year can fall back into the closed three-year period.

How it fits with the other clocks

If an examiner contacts you about a year that is more than three years old, the first question is which exception the IRS is relying on. If it is the six-year rule, ask for the computation. If there is no exception, the year may simply be closed.

Watch out for consents. An examiner working a six-year case may still ask for an extension on Form 872. Before you sign, know whether the period you are extending is really open. Extending a period that already expired can raise its own questions, but there is no reason to hand the IRS an argument.

Finally, keep records for the longer of the periods that might apply to you. If there is any chance a year falls under six years, three years of records is not enough.

The bottom line

The six-year rule is a numbers test: omitted gross income over 25 percent of the gross income stated on the return, with gross receipts as the base for a business, inflated basis counted as an omission, and adequately disclosed items left out. It also kicks in for omitted income over $5,000 tied to reportable foreign financial assets.

Do the math before you concede the point. A lot of six-year arguments do not survive a careful look at the return.