Form 8-K under U.S. securities law

In the United States, domestic companies must file a report called “Form 8-K” with the Securities and Exchange Commission (SEC) upon the occurrence of material corporate events. Material events fall into two categories: (1) those predefined by the SEC as material (listed below), and (2) those determined by the company itself to be material based on its own reasonable judgment (discretionary). Pursuant to Form 8-K, the following events all require filing: Category I: Business and Operations of the Issuer 1. Execution of a material agreement 2. Termination of a material agreement 3. Bankruptcy, liquidation, or receivership 4. Mine safety—reporting mine closures and violations Category II: Financial Information 1. Completion of an acquisition or disposition of assets 2. Operations 3. Results of operations and financial condition 4. Creation of financial liabilities or other off-balance-sheet liabilities 5. Acceleration of maturity of financial or off-balance-sheet liabilities 6. Costs associated with exiting or disposing of activities 7. Material adverse developments Category III: Equity Securities and Trading Markets 1. Notification of delisting, failure to meet continued listing requirements, or transfer of listing status 2. Unregistered sale of equity securities 3. Substantial changes to shareholders’ rights

At what time are earnings reports released? Use the SEC Form 8-K receipt time to verify pre-market/post-market labels.

In my backtest events, roughly half have unknown timing (i.e., the timing label is blank or marked as “intraday”). The backtesting engine defaults to treating all such events as pre-market and enters positions at market open on the announcement date. While this default may appear harmless, if a substantial proportion of these events are in fact announced post-market, the backtested returns will be systematically inflated. (Real-time trading is unaffected by this issue: live signals are only generated after EPS is officially released, making it impossible to buy before the announcement. The problem lies solely in backtest evidence—which, ironically, serves as the very basis for deciding whether to deploy the strategy in live trading.) Method: Assign timing to each event using the Form 8-K receipt timestamp. U.S. public companies releasing earnings must file a Form 8-K; the relevant item for earnings is Item 2.02. EDGAR records the exact second each filing is received. This timestamp represents the latest possible publication time: press releases may precede the 8-K, but never follow it. Each event undergoes four steps: 1. Identify the filing: Within a window defined by Eastern Time date—spanning from the trading day before the announcement date to the trading day after the entry date—select the original (non-amended) Form 8-K containing Item 2.02 that is closest in time to the event date. Do not use filingDate, because filings received after 17:30 ET are assigned a filingDate corresponding to the next business day. 2. Assign timing: Filings received before 9:30 ET are classified as pre-market; those between 9:30 ET and market close as intraday; and those at or after market close as post-market. Market close is typically 16:00 ET, but is 13:00 ET on half-days (e.g., the day after Thanksgiving or Christmas Eve). Receipts occurring on weekends or market holidays are assigned to the post-market period of the preceding trading day. 3. Compare with backtest entry time: If the 8-K is submitted before market open on the entry date, classify as “pre-entry”—this conclusion remains valid even if submission is delayed. If the 8-K is submitted at or after market close on the entry date, classify as “post-entry”; unless the press release predates the 8-K by a full trading session, such classification indicates look-ahead bias. 4. If no Item 2.02 is found: First search within the same window for other 8-Ks, 10-Qs, or 10-Ks; if still undetermined, examine price reaction (intraday move on announcement day and overnight gap). A precision threshold applies to price-based classification: for “pre-market” assignments, the Wilson lower bound of precision must reach 0.95; otherwise, the timing remains unclassified (“undetermined”). Round 1: I stratified events by year and daily dollar volume and sampled 200 timing-unknown events; 95 matched an Item 2.02 filing. Separately, I sampled 40 events each labeled “pre-market” and “post-market” as controls. Round 2: I timed all 3,203 remaining timing-unknown events (7,203 API requests, zero failures) and re-verified timing for all 3,585 already-timed events. Result 1: Approximately 60% of timing-unknown events were filed after market close. Among the 95 timing-unknown events matched to Item 2.02 in Round 1, 56 (58.9%, 95% CI: 48.9%–68.3%) were filed after market close on the backtest entry date; 8 were filed during market hours; and only 31 (32.6%) were confirmed filed before market open.

Olin Corporation Files Form 8K on October 28

3 days ago

Olin Corporation filed a Form 8K on October 28, 2026, disclosing regulatory information. Details are available via Investing.com for investors tracking stock performance.

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