MARKET VS LIMIT — TWO DOORS INTO THE MARKET

A market order buys speed and sells certainty; a limit order does the reverse. This course defaults to limit — here is the machinery that decides your fill. A market order is walking into the auction and shouting ‘sold!’ at whatever the current price is when your voice lands. A limit order is handing the auctioneer a card before it starts: ‘up to this much, not a cent more.’ With the card you might go home empty-handed — but you will never discover, in the excitement, that you paid double.

ORDERS I · STAGE 2 · LESSON 4

THE TAKEAWAYS

• The book: every market carries standing limit orders — bids stacked below, asks stacked above. A market order consumes the best of them instantly; a limit order joins the queue at your price and waits its turn.
• Context decides the toll: on SPY shares in regular hours the spread is usually a penny (State Street's 30-day median spread rounds to 0.00% of price — Stage 1), so a market order's toll there is small. On options the spreads are dimes, not pennies, and the same habit costs real money.
• The midpoint — (bid + ask) ÷ 2 — is where this course starts every limit order, walking a few cents toward the other side only if the trade still makes sense a little worse. Stage 5's chain lesson turns that into a routine.
• When is a market order acceptable? At most, when all of these hold at once: regular hours, a penny-class spread, no news pending, shares rather than options — and even then, a limit order priced at the market does the same job with a seatbelt fitted.

WORKED EXAMPLE — STEP BY STEP

1. The real quote (Oct 9, 2026, about 12:05pm CT): SPY's 773 call — bid 20.53, ask 20.68. Spread = 0.15. Midpoint = (20.53 + 20.68) ÷ 2 = 20.605, call it 20.61. The graphic draws the book around it.
2. Door one, a market buy: it fills at the best ask, 20.68 — $2,068 per contract. You have crossed the entire spread at entry; sell instantly at the bid and you'd receive 20.53. The round trip burned $15 per contract before the idea had a chance to be right.
3. Door two, a limit buy at the midpoint, 20.61: if it fills, you saved $7 versus the ask — half the spread — and the same habit on exit saves the other half. Multiplied over a journal of paper trades, this is the cheapest edge in the whole course.
4. The limit's honest cost: it may not fill. SPY runs upward, your order sits at 20.61, and the trade happens without you. Count that cost correctly: a missed trade costs $0. A chased trade pays the spread and the slippage — and usually arrives at the top anyway.
5. Scale the habit up: Stage 5's chain routine — scan delta, check theta and IV, walk a limit from the midpoint — exists because every leg of this arithmetic repeats on every trade you will ever place. Order type is not a preference. It is a recurring cost line.

WHY ‘BEST AVAILABLE PRICE’ HAS FINE PRINT

Brokers owe you best execution, and exchange rules protect the best displayed quotes — the NBBO, the national best bid and offer. But protection covers the displayed price at the moment your order arrives, not the price on your screen when you decided. In a fast market the book changes between your click and your fill; in a thin market the ‘best available’ may be one small quote with far worse prices standing behind it (that's slippage, Lesson 6). A limit order replaces all of that uncertainty with a single number you chose yourself. That is the whole argument, and it's why this course chooses certainty of price over certainty of fill — every time.

COMMON BEGINNER MISTAKES

• Market-ordering options — paying the full ask in and the full bid out, then blaming the spread for the result.
• Parking a limit order so far from the market that it can only fill once the trade has already gone wrong. A stale bargain is a magnet for bad news.
• Chasing: cancelling a working limit and re-pricing it worse, twice, three times — paying the discipline away in instalments.
• Using market orders in the first minutes after the open, or into a news release, exactly when spreads are at their widest.

CHECK YOURSELF

DO IT — PLACE BOTH DOORS ON PAPER

In a paper account, pick SPY and place two paper orders for 1 share: a market order, and a limit order priced at the midpoint of the current bid/ask. Screenshot both outcomes — the market order's fill report and the limit order filled or still working — and journal the quoted spread, each order's fate, and the fill price versus the quote you saw. Cancel anything still working. Lesson 6 teaches you to read those fill reports properly.