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BlogPublished June 19, 2026 · 15 min read

Liquidity and the Bid-Ask Spread When Selling Options

Illustration of financial data representing liquidity and the bid-ask spread
A wide bid-ask spread is a hidden tax on every option trade—liquidity decides how much you keep.

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.

The bid-ask spread is a hidden cost

When you sell an option you receive the bid; when you buy it back you pay the ask. The gap between them is lost to the spread, and it is paid twice over a full round trip. On a liquid option the spread might be a few cents; on an illiquid one it can be a meaningful fraction of the premium itself.

A quick example on a $1.50 option:

  • Liquid — bid $1.48 / ask $1.52, midpoint $1.50, spread $0.04 (~3%)
  • Illiquid — bid $1.30 / ask $1.70, midpoint $1.50, spread $0.40 (~27%)
  • Sell the illiquid one at the bid and you start down $0.20 vs. fair value
  • Buy it back at the ask and you lose another chunk—on both ends

That 27% spread doesn't show up as a separate fee—it just means a worse fill. Over many trades, the drag rivals commissions, and it lands directly in your return on capital.

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.

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.

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