Mark vs Last vs Bid/Ask: Why Your Options P&L Looks Wrong
Your option shows a tidy gain, you go to sell, and the fill is worse. You're not being cheated — you're looking at three different prices that only sometimes agree.
NoVo Options Trading ·
Open an options position and your platform shows several prices at once. They measure different things, and confusing them is why your P&L can look better (or worse) than what you can actually get.
The three numbers
Bid / Ask. The best price someone will buy from you (bid) and sell to you (ask) right now. This is what you can actually transact at — the real, tradable price. Mark. Usually the midpoint of the bid and ask. Brokers use the mark to value your open positions, so your unrealized P&L is calculated off the mark, not off what you'd get selling into the bid. Last. The price of the most recent actual trade. On a thin strike, the last trade could be minutes old and far from the current market — a stale number.
Your P&L is marked to the mid; your exit fills at the bid. On a wide strike, that gap is the surprise.
Why the P&L looks wrong
If your position is marked at the 1.25 mid but the bid is only 1.15, selling gives you 1.15 — a dime worse than the P&L implied, because you cross half the spread to exit. On a wide or thin strike that difference is real money. The mark is a fair-value estimate, not a guaranteed exit.
The takeaway
Trust the bid/ask for what a trade will really cost or return, treat the mark as an estimate of fair value, and be skeptical of a stale last on illiquid strikes. Trading liquid, near-the-money SPY strikes keeps all three numbers close together — which is exactly what you want when a scalp comes down to pennies.
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NoVo is a software tool for market analysis, not financial advice. This article is general education, not investment advice. Options trading involves substantial risk of loss, up to and including your entire capital. NoVo makes no guarantee of profit, win rate, or performance, and past results do not predict future outcomes. You are responsible for your own broker account, configuration, and trading decisions.
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