Placing the order: market, limit and the traps

Why is this important?

Ten lessons have been about what to trade. None have been about how the trade actually reaches the exchange, and that gap is where beginners lose their first avoidable money. Not on a wrong view: on a wrong button.

Here is what makes options different from buying a stock. In a liquid stock, the best buying price and the best selling price sit a paisa apart, so pressing "market" costs you nothing worth naming. In options, those two prices can sit 20% apart on a quiet strike. That gap has a name — the bid-ask spread — and it is not a statistic. It is a toll booth every order drives through, and you choose the lane. Lesson 15 will show you the same number sitting in a column of the NSE option chain; today it comes out of your account.

Real market example

Rahul finished Lesson 10, paper traded for a month, and is placing his first real order: one lot of the NIFTY 25,000 CE, quoted at ₹120. He opens the depth window (his broker calls it "market depth"; the exchange calls it the order book) and sees this:

A healthy strike: ₹0.40 between best bid and best ask, thousands of units stacked on both sides. A market order here fills at ₹120.20 and costs him ₹0.40 × 65 = ₹26 against the mid-price. A rounding error. Rahul presses market, fills instantly, and nothing bad happens — which is exactly how the habit gets learned.

Two weeks later he uses the same reflex on a 25,800 CE in the next month's expiry: a far, forgotten strike. The depth window looks nothing alike.

The last traded price still reads ₹5.20, so the position "looks" like ₹338. He presses market. He is filled at ₹6.50 — ₹422 — and the moment he owns it, the only price anyone will buy it back at is ₹4.05, or ₹263. He is down ₹159, about 38%, on a view that has not yet been right or wrong. That gap is slippage; the part his own order caused by eating into a thin book is impact cost.

A limit order at ₹5.20 risked something much cheaper: not filling at all.

Third scene, and the one that charges the highest tuition. Rahul buys the 25,000 CE at ₹120 and protects it with a stop loss at ₹95. Two days later NIFTY gaps down at the open and the strike opens quoted around ₹61. His SL was a limit order at ₹95, so it triggers and joins a queue at ₹95, where no buyer will ever stand again. It sits there, unfilled and useless, while the premium drifts to ₹48. Had he used SL-M, he would have been out near ₹60: a worse price than he wanted, and about ₹780 better than what actually happened.

Key concepts

• Market order: take whatever the book offers, right now. Guarantees a fill, guarantees nothing about price. Fine on the ATM weekly strike, expensive-to-reckless everywhere else.
• Limit order: "this price or better." Guarantees the price, guarantees nothing about the fill. The correct default in options, and the reason to place it at the ask rather than at the last traded price when you actually want to be filled.
• SL (stop loss): a trigger price which, when touched, releases a limit order. Protects your exit price, and can leave you holding the position in exactly the fast market you were trying to escape.
• SL-M (stop loss market): the same trigger releasing a market order. Always gets you out, sometimes at a price that stings. In a gap, the sting is the cheaper outcome.
• GTT (good till triggered): a resting instruction parked at your broker — not at the exchange — for up to a year. It watches for your trigger and only then sends a real order. Excellent for "buy the Reliance 1,400 PE if it ever reaches ₹40"; poor as a stop in a fast move, because it fires after the price prints.
• Cover order: an entry carrying a compulsory stop loss you can tighten but never remove. Bracket order: entry, target and stop on one ticket. Several Indian brokers withdrew bracket orders after the 2020 peak-margin rules, so check what yours still supports instead of assuming.
• Freeze quantity: the largest single order NSE accepts in one contract — roughly 1,800 units on NIFTY, about 27 lots at a 65 lot size. It caps the order, not the position: anything bigger is rejected outright and you split it yourself. NSE revises the number periodically, so trust the current circular over this sentence.
• Slippage: the difference between the price you expected and the price you got. Impact cost is the slice of that gap your own order size created.

Visual explanation

The whole order ticket in one table. Read the middle two columns together, because they are the entire idea: every order type guarantees exactly one of price or execution, never both.

The last row is the honest one. Cover orders exist because the most common reason a stop loss fails is not the market. It is the trader cancelling it.

How traders use it

• Limit by default, market by exception. Place the limit at the ask (buying) or the bid (selling) and you get a near-instant fill with a known worst price. That one habit removes most slippage without costing you fills.
• Read the spread as a percentage, never in rupees. ₹0.40 on a ₹120 option is 0.3%. ₹2.45 on a ₹5.20 option is 47%. A workable personal rule: if crossing costs more than 1% of the premium, use a limit and be patient; if it costs more than 5%, ask whether the strike deserves your money at all.
• Size against the depth, not against your account. If the entire visible book is 195 units and you want 650, you are the market and the quoted price is fiction. This is a liquidity ceiling on position size, and it sits underneath every sizing rule in Lesson 30.
• Split around the freeze quantity deliberately. Five orders of 20 lots beat one rejected order of 100 — but each slice nudges the price, so slice into a calm market, never into the last ten minutes of expiry day.
• Give exit orders more care than entry orders. You choose when to enter. The market chooses when you must exit, and it invariably chooses a fast, thin, ugly moment. That is exactly why SL-M is usually the right stop on a position you cannot babysit.
• Journal the fill, not just the plan. Lesson 10's journal records why you entered. Add two columns: the price you intended and the price you got. A month of that gap, totalled, is the most surprising number most new traders ever compute about themselves.

Common mistakes

• Pressing market on a thin strike. The most expensive reflex in retail options. The screen shows the last trade; you pay the ask; on a far strike those are different worlds.
• Trusting the last traded price. LTP is history, possibly from forty minutes ago on a quiet strike. Bid and ask are the present tense. Trade the present tense.
• Using SL where you needed SL-M. A limit stop in a gapping market is a stop that politely declines to save you.
• Setting the stop on the premium when the thesis was about the index. "Exit if NIFTY closes below 24,900" and "exit if the premium halves" are different trades. Decide which you actually mean, and write down which it was.
• Panicking at a rejection. "Freeze quantity exceeded", "insufficient margin", "contract not permitted", "blocked by RMS" — one-line problems with one-line fixes, not the broker refusing you. Read the message; it names the thing to change.
• Chasing a missed limit with a market order. The trade that got away costs nothing. The market order placed in irritation costs the spread and, usually, the entry you were annoyed about missing.
• Forgetting that a round trip crosses the spread twice. Every quoted spread is paid once entering and once leaving, out of the same premium your profit has to grow from.

Quiz

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