Schedule C's 6-Year Audit Window: What "25% of Gross Income" Actually Means

Published: August 25, 2026 · Reading time: 11 min

TL;DR: The IRS's default audit window is 3 years (§6501(a)), stretching to 6 years if you omit more than 25% of gross income (§6501(e)(1)(A)(i)). For a trade or business, the statute defines "gross income" for that test as total gross receipts before cost of goods sold is subtracted (§6501(e)(1)(B)(i)) — a bigger, different number than Schedule C's own Line 7 "Gross income," which is already net of COGS. And overstating your cost of goods sold — inflating basis on inventory or resold goods — counts as an omission on its own (§6501(e)(1)(B)(ii)), a rule Congress wrote in 2015 after the Supreme Court's Home Concrete decision, and one the disclosure exception does not cover.

Every guide to record retention repeats the same three numbers: three years, six years, forever. Almost none of them explain what "25% of gross income" is measured against — and for a Schedule C filer with any cost of goods sold, that gap is not academic. The statute's own definition of "gross income," written specifically for a trade or business, is not the number printed on Schedule C Line 7.

Three Windows, One Statute

IRC §6501 sets three different assessment periods, and which one applies depends entirely on what was omitted or misstated.

The 3-year and unlimited windows are well understood. The 6-year window is where the confusion lives, because "gross income" sounds like a term everyone already knows — and on Schedule C, it's printed right there on Line 7.

The Trap: Schedule C's "Gross Income" Isn't the Statute's "Gross Income"

Schedule C builds its own income figure in several steps:

Line 7 is labeled, in plain IRS print, "Gross income." So it's a completely reasonable assumption that when the tax code says "25% of gross income," it means 25% of that same Line 7 figure. It doesn't.

§6501(e)(1)(B)(i) defines the term for this specific purpose: "In the case of a trade or business, the term 'gross income' means the total of the amounts received or accrued from the sale of goods or services (if such amounts are required to be shown on the return) prior to diminution by the cost of such sales or services."

Read that again: prior to diminution by the cost of such sales or services. The statutory denominator is gross receipts before cost of goods sold comes out — essentially Schedule C's Line 1, not Line 7. For a service freelancer with no inventory, Lines 1 and 7 are usually the same number and the distinction never bites. For anyone with meaningful cost of goods sold — a reseller, an Etsy seller, a maker who buys materials — the two figures diverge, and the divergence changes the math.

Worked Example: The Same Omission, Two Different Answers

A freelance reseller reports $150,000 of gross receipts (Line 1) and $70,000 of cost of goods sold (Line 4), no returns/allowances and no other income, for Line 5 and Line 7 both equal to $80,000. An IRS examination later finds $22,000 of gross receipts — cash sales — that were never reported at all.

Benchmarked against Line 7, this omission looks like it opens the 6-year window. Benchmarked correctly, against the statute's own pre-COGS definition, it doesn't come close — the return stays on the ordinary 3-year clock. Getting the denominator wrong here doesn't just misstate a percentage; it misstates how long the return is actually exposed.

The reverse mistake is just as real: a service freelancer with no COGS at all sees Line 1 and Line 7 converge, so for them the naive shortcut happens to give the right answer — which is exactly what makes the trap easy to miss until a filer with real cost of goods sold runs the same math.

The Other Half: Overstating Cost of Goods Sold Is Its Own Omission

The example above assumes the reseller's $70,000 cost of goods sold figure was accurate. What if it wasn't?

Colony, then Home Concrete, then Congress

In Colony, Inc. v. Commissioner, 357 U.S. 28 (1958), the Supreme Court considered a taxpayer who had overstated the basis of land it sold, understating its gain. The Court held that overstating basis is not an "omission from gross income" for purposes of the (then-materially-identical) 6-year rule — the sale itself was disclosed on the return; only the cost side was wrong, and the IRS was in no special position of disadvantage in catching that kind of error.

For decades, the IRS disagreed with that outcome and tried to reverse it by regulation. In United States v. Home Concrete & Supply, LLC, 566 U.S. 478 (2012), the Supreme Court held that a Treasury regulation could not override Colony's reading of the statute — if the rule was going to change, Congress had to change it.

Congress did exactly that. The Surface Transportation and Veterans Health Care Choice Improvement Act of 2015 (Pub. L. 114-41, §2005) added what is now §6501(e)(1)(B)(ii): "An understatement of gross income by reason of an overstatement of unrecovered cost or other basis is an omission from gross income." The amendment applies to returns filed after July 31, 2015, and to any earlier return whose assessment period hadn't already expired by that date.

The practical result for a Schedule C filer in 2026: inflating the cost of goods sold you claim on Line 4 — overstating what you actually paid for inventory or resold goods — now counts as an omission from gross income in its own right, separate from any unreported receipts.

Worked Example: No Receipts Omitted, Still Over 25%

A different reseller reports $90,000 of gross receipts (Line 1) — every dollar accurately. But the $50,000 of cost of goods sold claimed on Line 4 turns out, on examination, to be overstated: the true, substantiated cost basis of the goods actually sold was only $26,000.

$24,000 is more than 25% of the $90,000 stated on the return, so the 6-year window applies — even though every gross receipt was reported correctly and completely. No cash sale went unreported; the entire exposure comes from the cost side of the ledger.

Disclosure Usually Cures an Omission — Except This One

For an ordinary omitted item, the statute gives you an out. §6501(e)(1)(B)(iii) says an amount isn't counted as "omitted" for the 25% test if it's "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 such item." Report a gray-area item honestly, describe it clearly, and it stops counting toward the 25% threshold at all.

That exception has a carve-out written into the same sentence: it applies to every omission "other than in the case of an overstatement of unrecovered cost or other basis." Disclosure cures an unreported receipt. It does not cure an inflated cost-of-goods-sold basis. If your Line 4 figure is wrong, attaching a statement explaining the number doesn't take it out of the 25% calculation — the overstatement counts regardless of how transparently you presented it.

A Separate Trigger: Foreign Assets Skip the Percentage Test Entirely

One more 6-year trigger has nothing to do with the 25% math. §6501(e)(1)(A)(ii), added by the HIRE Act of 2010, gives the IRS 6 years if an omitted amount is attributable to a specified foreign financial asset reportable under §6038D (generally on Form 8938) and exceeds $5,000 — full stop, regardless of what fraction of total gross income that represents. A freelancer with substantial U.S. gross receipts who fails to report a relatively small amount of income tied to a foreign account or platform can trigger this window on a dollar amount that would never come close to 25% of anything. See Schedule C for freelancers living abroad and Schedule C for foreign clients and withholding for how foreign-source income interacts with the rest of the return.

Quick Reference

None of this changes what you owe. It changes how long the number you filed stays open to question — and whether the receipts and cost basis behind your Line 4 figure need to survive three years or six.

Frequently Asked Questions

Does the IRS's 6-year audit window for Schedule C use my Line 7 gross income or my Line 1 gross receipts?

Neither line label controls directly — the statute defines its own term. IRC §6501(e)(1)(B)(i) says that for a trade or business, "gross income" for purposes of the 6-year rule means the total amount received or accrued from the sale of goods or services, before any reduction for the cost of those sales. That is a bigger number than Schedule C's own Line 7 (which is already net of Line 4 cost of goods sold) — it's closer to Line 1, gross receipts. A preparer who benchmarks the 25% test against Line 7 gross income rather than Line 1 gross receipts is using the wrong, smaller denominator, which can make an ordinary omission look far more dangerous than the statute actually treats it.

If I omit some income from my Schedule C, when does the IRS get 6 years instead of 3 to audit me?

Under IRC §6501(a), the default assessment window is 3 years from the later of your filing date or the return's due date. IRC §6501(e)(1)(A)(i) extends that to 6 years if you omit from gross income an amount that exceeds 25% of the gross income stated on the return. For a Schedule C filer, that 25% test is measured against gross receipts before cost of goods sold is subtracted — the §6501(e)(1)(B)(i) definition — not against net profit, not against AGI, and not against Schedule C's own Line 7. A freelancer who underreports cash income has to omit more than a quarter of total gross receipts, not a quarter of net income, before the 6-year window opens.

Does overstating my cost of goods sold count as an omission from gross income?

Yes, and this is a fairly recent and frequently misunderstood rule. In Colony, Inc. v. Commissioner (1958), the Supreme Court held that overstating the basis or cost of property sold does not count as an "omission from gross income" under the materially identical predecessor statute, because the sale itself was fully disclosed on the return. In United States v. Home Concrete & Supply, LLC (2012), the Court held that Colony's interpretation still controlled under the statute as written at that time, rejecting a Treasury regulation that tried to reverse it administratively. Congress then did what the Court said only Congress could do: the Surface Transportation and Veterans Health Care Choice Improvement Act of 2015 added §6501(e)(1)(B)(ii), which states directly that an understatement of gross income caused by overstating unrecovered cost or basis IS an omission from gross income. So today, inflating your Schedule C cost of goods sold — claiming a higher basis for inventory or resold goods than you can substantiate — can trigger the 6-year window on its own, even if every dollar of gross receipts was reported accurately.

Can I protect myself from the 6-year window by disclosing an omitted item on my return?

Usually, yes — but not for a basis overstatement. IRC §6501(e)(1)(B)(iii) says an item is not treated as omitted, for purposes of the 25% test, if it's disclosed on the return or in an attached statement in a way that's adequate to apprise the IRS of its nature and amount. That protection applies to an ordinary omitted item, like unreported income you flagged in a statement. But the same subsection carves out basis overstatements by name — the disclosure exception explicitly does not apply "in the case of an overstatement of unrecovered cost or other basis." Attaching a note explaining an inflated cost-of-goods-sold figure does not neutralize it the way disclosing unreported income would.

Does a foreign bank account or asset change my Schedule C audit window?

It can, independent of the 25% test entirely. IRC §6501(e)(1)(A)(ii), added by the HIRE Act of 2010, gives the IRS 6 years if an omitted amount is attributable to a specified foreign financial asset reportable under §6038D (generally on Form 8938) and exceeds $5,000 — regardless of what percentage of your total gross income that $5,000 represents. A freelancer with substantial U.S. gross receipts who fails to report income routed through, or earned from, a foreign account or platform can trip this 6-year window on a relatively small dollar amount, even in a year where the 25%-of-gross-receipts test would never have been close.

Authoritative References

• 26 U.S.C. §6501 — Limitations on assessment and collection
• 26 CFR §301.6501(e)-1 — Omission from return
• Colony, Inc. v. Commissioner, 357 U.S. 28 (1958)
• United States v. Home Concrete & Supply, LLC, 566 U.S. 478 (2012)
• IRS — Instructions for Schedule C (Form 1040)
• IRS — About Form 8938, Statement of Specified Foreign Financial Assets

Related reading: Schedule C Line 1: Gross Receipts · Schedule C Line 7: Gross Income · Schedule C Audit Triggers · IRS Receipt Retention Rules

The Records That Make the Right Denominator Provable

Whichever window applies to your return, it only helps you if the numbers behind Line 1 and Line 4 are backed by real receipts — the sale, and the cost of what you sold. CentSense scans every receipt with AI, tags it to the right Schedule C line, and keeps the purchase cost of your inventory or materials tied to the sale it supports, so your gross receipts and your cost of goods sold are both defensible years later. Free tier includes 10 AI scans per month; Solo is $5/month for unlimited scanning and mileage logging.

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This guide is general education for U.S. freelancers and Schedule C filers covering the 2026 tax year. It is not personalized tax advice. Statute-of-limitations questions are fact-specific and can turn on details — such as the exact date a return was filed or amended — not covered here. Consult a CPA or EA about your specific situation.