The underlying — SPY the ETF — stops regular-hours trading at 4:00 PM ET. The options have a wrinkle: broad-based ETF options like SPY, QQQ and IWM have historically had a slightly later options cutoff than single-stock options, which stop at 4:00. The exact last-trade minute is a detail your broker sets and can change, so confirm it with your platform rather than trusting a number you read once.

Why the exact minute matters

On a 0DTE contract, expiration is today. If you're holding into the final minutes, you're choosing between closing the position and letting it settle. Anything $0.01 in-the-money at expiration is automatically exercised — which for a long call means being handed 100 shares you have to pay for. The last-trade cutoff is your final chance to avoid that by selling to close.

The safe rule ignores the trivia: be flat by 4:00. You never have to hold a same-day option into the settlement window.

The rule that removes the question

Serious 0DTE scalpers don't play the cutoff — they're flat by the close, usually well before it, because the last stretch is thin, wide, and dominated by decay. If you're out by 4:00, the 4:00-vs-4:15 debate never touches you, and neither does an in-the-money expiration you can't afford. This is one reason NoVo attaches a full exit ladder and keeps a one-click close at hand, rather than leaving you to the settlement roulette.