8-K vs 10-K: Event Report Within Four Business Days or the Audited Annual Report

The short version

An 8-K tells you something happened. A 10-K tells you, a few weeks after the year ends, what the whole year added up to, with an auditor's opinion on the numbers. The 8-K is fast and narrow. The 10-K is slow, complete and carries more legal weight.

The same event usually appears in both: first as an 8-K within days, then inside the 10-K's financial statements, notes and exhibit list. The individual 8-K items are covered in 8-K item codes explained; this guide is about how the two forms relate.

Event report versus periodic report

The 8-K is event-driven. Under General Instruction B.1 of Form 8-K, a report is due within four business days after an event listed in Sections 1 to 6 and 9 of the form, unless an item says otherwise. If nothing in the list happens, no 8-K is required.

The 10-K is periodic. Exchange Act Rule 13a-1 requires an annual report for each fiscal year, and General Instruction A of Form 10-K sets the deadline: 60 days after the fiscal year end for large accelerated filers, 75 days for accelerated filers and 90 days for everyone else. The 10-Q and 10-K deadlines table shows which companies fall into which group. The quarterly 10-Q sits between the two. Under General Instruction B.3 of Form 8-K, information already reported does not need to be reported again on an 8-K.

Audited, certified and signed

What separates the 10-K most clearly is the checking behind it.

• Audited financial statements. Item 8 of Form 10-K requires financial statements meeting Regulation S-X, which for annual statements means an audit and a report from an independent registered public accounting firm. An 8-K earnings release under Item 2.02 is normally unaudited.
• Signatures. General Instruction D(2)(a) of Form 10-K requires signatures from the registrant's principal executive officer, principal financial officer, controller or principal accounting officer, and at least a majority of the board. An 8-K is signed on behalf of the registrant by one duly authorized officer.
• Certifications. Rule 13a-14 requires the principal executive and principal financial officers to sign certifications filed as exhibits to every 10-K and 10-Q. These are the Sarbanes-Oxley Section 302 and 906 certifications, filed as Exhibits 31 and 32. An 8-K carries neither.

Part III of a 10-K (directors, executive pay, ownership, related transactions and auditor fees) may be left out and incorporated by reference from the proxy statement, but only if that proxy is filed within 120 days after the fiscal year end, under General Instruction G(3). Otherwise the information must arrive in the 10-K or an amendment by the end of that 120-day period.

Filed versus furnished

General Instruction B.2 of Form 8-K says information furnished under Item 2.02 (results of operations) or Item 7.01 (Regulation FD) is not deemed "filed" for purposes of Section 18 of the Exchange Act, unless the company says otherwise or incorporates it by reference into another filing. Section 18 is the provision that creates liability for false or misleading statements in filed documents.

So the earnings press release attached to an Item 2.02 8-K is furnished, while the audited statements in the 10-K are filed. The release often comes first and the numbers usually match, but the 10-K is the one the company files as its financial statements of record.

Exchange Act Rule 13a-11(c) adds that failing to file an 8-K required solely under Items 1.01, 1.02, 1.05, 2.03, 2.04, 2.05, 2.06, 4.02(a), 5.02(e) or 6.03 is not by itself a violation of Rule 10b-5. The duty to report still exists.

The 10-K catches what the 8-Ks missed

Item 9B of Form 10-K, "Other Information", requires a company to disclose any information that should have been reported on an 8-K during the fourth quarter but was not. If it is disclosed there, it does not have to be repeated on an 8-K. Some companies also use Item 9B for events after year end, stating that the disclosure is made in lieu of an 8-K.

The flow also runs backwards. If a company concludes that previously issued annual financial statements should no longer be relied upon, it reports that on an 8-K under Item 4.02, and the restated figures normally follow in an amended 10-K or the next annual report. And General Instruction B.4 of Form 8-K notes that agreements need not be attached to an 8-K unless the item requires it, but they must still be filed as exhibits to registration statements and periodic reports under Item 601 of Regulation S-K, which is why a 10-K exhibit index often cites earlier 8-Ks.

A real pair: one year, three filings

Fennec Pharmaceuticals (FENC) has a calendar fiscal year and checks the non-accelerated filer box on its 10-K cover.

The event. On Thursday, November 13, 2025, the company entered into an underwriting agreement for 4,666,667 common shares at $7.50, with a 30-day option for 700,000 more. The Item 1.01 8-K was filed on Monday, November 17. Friday, November 14 was business day 1 and Monday was day 2. The four-business-day deadline was Wednesday, November 19.

The annual figures. The 10-K's Note 6 reports the same offering after the fact: 5,367 thousand shares including the 700 thousand option shares, for gross proceeds of about $40.25 million. That matches the 8-K: 4,666,667 + 700,000 = 5,366,667 shares, and 5,366,667 × $7.50 = $40,250,002.

The earnings release against the 10-K. On Tuesday, March 24, 2026, the company furnished its full-year results under Item 2.02. The 10-K followed on Friday, March 27, four days before the 90-day deadline of March 31, 2026 (31 + 28 + 31 days after December 31).

From the filing

Form 8-K

“The selected financial data presented below is derived from our unaudited condensed consolidated financial statements, which were prepared in accordance with U.S. generally accepted accounting principles.”

Several figures changed between the two documents:

Revenue did not change; expenses and tax did. This guide does not infer why. The release was labelled unaudited, and the audited 10-K is the version that was filed.

How to check a company on Signal8

• The live SEC filings feed shows 8-Ks and 10-Ks as EDGAR accepts them, with the 8-K item numbers on each row.
• A company's filings tab, for example FENC's filings, lists every 8-K and 10-K for that issuer in one place.
• Alerts can notify you when a company on your watchlist files an 8-K or its annual report.
• How to find the latest 10-K, 10-Q and 8-K explains filtering by form and spotting amendments.

The form texts are on sec.gov: Form 8-K and Form 10-K. Rule 13a-11 is on eCFR.

FAQ