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BlogPublished June 19, 2026 · 17 min read
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Liquidity and the Bid-Ask Spread When Selling Options
Options liquidity and the bid-ask spread: how to read open interest, volume, and spread width, why illiquid strikes quietly cost sellers, and how to find tradeable strikes.
Two strikes can show the same premium on the screen, yet one hands you most of it and the other quietly skims a third off the top. The difference is liquidity.
The bid-ask spread is the gap between what buyers will pay and what sellers will accept. On illiquid options it is wide, so you sell below the midpoint and buy back above it: a hidden tax paid on every round trip.
This guide explains options liquidity and the bid-ask spread for sellers: how to read open interest, volume, and spread width, why illiquid strikes cost you, and how to find strikes you can actually trade. This is education, not investment advice.
You will learn how the bid-ask spread works, how open interest and volume signal liquidity, and how to spot tradeable strikes on the options chain.
Reading liquidity: open interest and volume
Two columns on the options chain tell you how liquid a contract is. Open interest is the number of contracts currently outstanding; volume is how many traded today. High numbers mean many participants, tighter spreads, and easier fills near the midpoint.
What the numbers signal:
- Open interest: standing contracts; depth of the market at that strike
- Volume: today's activity; confirms the strike is actively traded
- High OI + tight spread: you'll likely fill near the midpoint
- Low OI + wide spread: fills are poor and exits can be painful
Where to find these columns and how to read the rest of the chain is in how to read an options chain for sellers.
Why illiquid options hurt sellers most
Sellers are especially exposed to liquidity because they almost always have to trade twice: once to open and often once to close or roll. Each trip pays the spread, and an illiquid strike can also be hard to exit at all when you most need to, like during a fast move.
The compounding problems:
- Round-trip spread cost is paid on both the open and the close
- Rolling a position adds even more spread crossings
- In a fast move, illiquid strikes can gap or freeze: no good exit
- Wide markets make defined-risk spreads (four legs) especially costly
This is why multi-leg trades like the iron condor demand liquid underlyings: four legs mean four spreads to cross.
What the spread actually costs you, in dollars
“Wide spread” stays abstract until you price it. Take the same short put sold for a $1.50 mid on 3 contracts, and vary only the quality of the market. Assume you give up half the spread getting in and half getting out: the realistic outcome when you are not patient with limit orders.
| Market | Spread | Round-trip cost | % of premium collected |
|---|---|---|---|
| Very liquid (SPY-like) | $1.48 / $1.52 (0.03) | ~$12 | ~2.7% |
| Normal large cap | $1.45 / $1.55 (0.07) | ~$30 | ~6.7% |
| Thin name | $1.30 / $1.70 (0.27) | ~$120 | ~26.7% |
| Very illiquid | $1.05 / $1.95 (0.60) | ~$270 | ~60% |
The bottom row is the one to internalise: on a genuinely illiquid strike, the spread can consume more of your edge than commissions, taxes and a losing trade combined. And it compounds, a seller who rolls every cycle pays that toll several times a year on the same position (how to roll options), which is why liquidity belongs in your entry checklist, not in your list of things to worry about later (expectancy vs. win rate).
One practical screen: divide the spread by the mid. Under ~5% is comfortable, 5–10% deserves a limit order and patience, and above ~15% the strike is usually not worth selling at any premium, the exit will cost you what the entry paid you.
How to find tradeable strikes
A practical liquidity checklist:
- Trade options on liquid underlyings: major ETFs and large-cap names
- Look for open interest in the hundreds or thousands at your strike
- Keep the spread to a small percentage of the premium (single digits)
- Use limit orders at the midpoint, never market orders on options
- Favor standard monthly expirations, which concentrate liquidity
Index and ETF products are popular with sellers partly for their deep liquidity. See SPY vs. SPX vs. single stocks. Always work your order with a limit price; a market order on a wide option is how sellers donate to market makers.
Conclusion: liquidity is part of the edge
Key takeaways:
- The bid-ask spread is a hidden cost paid on every round trip
- Open interest and volume reveal how liquid a strike is
- Sellers pay the spread twice, and may struggle to exit illiquid strikes
- Trade liquid names, check OI, and always use midpoint limit orders
Educational only, not personal financial advice. More in the blog · Request access.
Frequently asked questions
- What is the bid-ask spread on an option?
It is the gap between the highest price buyers will pay (the bid) and the lowest sellers will accept (the ask). Sellers receive the bid to open and pay the ask to close, so the spread is a cost paid on each trade.
- How do I know if an option is liquid?
Check open interest and volume on the chain, and the width of the bid-ask spread. High open interest, active volume, and a spread that is only a few percent of the premium signal a liquid, tradeable strike.
- Why does liquidity matter more for option sellers?
Sellers usually trade twice, open and then close or roll, so they pay the spread on each leg. Illiquid strikes also become hard to exit during fast moves, exactly when you most need out.
- Should I use market orders on options?
No. Market orders on options can fill far from fair value, especially on wide spreads. Use limit orders near the midpoint and work the price: a market order on an illiquid option is a gift to market makers.
- What open interest is enough to sell an option?
There is no hard rule, but open interest in the hundreds or thousands at your strike, with active daily volume and a tight spread, generally means you can fill near the midpoint and exit cleanly.
- How wide is too wide for a bid-ask spread?
Divide the spread by the mid price. Under roughly 5% is comfortable, 5–10% calls for a patient limit order, and above about 15% the strike is usually not worth selling: the round trip can hand back a quarter or more of the premium you collected.
- Does the bid-ask spread cost me twice?
Yes, if you close the position: you typically concede part of the spread entering and again exiting. Letting an option expire worthless avoids the exit cost, which is one practical reason sellers of thin strikes prefer expiration to buying back.
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