Cash-secured puts, risk first: what you agree to buy and what it can cost
Selling a cash-secured put means promising to buy 100 shares at the strike. Payoff table, breakeven, assignment, gap risk, costs and a pre-trade checklist.
Key points
- Selling a put is a promise to buy 100 shares per contract at the strike; cash-secured means holding strike x 100 in cash.
- Illustrative: stock at $50, sell the $45 put for $1.10. Breakeven $43.90, maximum gain $110, maximum loss $4,390.
- US equity options are generally American-style, so a short put can be assigned early, especially when deep in the money.
- A cash-secured put has the same basic payoff shape as a covered call: capped gain, nearly all of the stock's downside.
- Only sell a put at a strike where you would buy the stock today, sized by the loss you can take, never by the premium.
A cash-secured put is often described as a way to get paid while you wait to buy a stock at a lower price. The risk-first description: you are agreeing in advance to buy 100 shares at a fixed price, even if the stock has collapsed by the time you have to pay. The premium is your fee for that promise.
What you agree to
When you sell (write) a put, the buyer gets the right to sell you 100 shares of the underlying stock at the strike price, any time until expiration. You receive the premium up front. Your side of the contract is an obligation, not a choice: if the put is exercised and assigned to you, you buy 100 shares per contract at the strike, whatever the market price is at that moment.
Standard US equity option contracts cover 100 shares, and premiums are quoted per share, so a quote of $1.10 is $110 per contract before costs. Corporate actions can create adjusted contracts with different terms.
"Cash-secured" means you hold enough cash in the account to pay for the shares if you are assigned. The amount is simple:
- Cash set aside = strike price x 100 x number of contracts.
For one $45 put, that is $4,500. Treat it as spoken for until the put is closed, expires or is assigned.
The payoff at expiration
Illustrative example: a stock trades at $50.00. You sell one put with a $45 strike for a premium of $1.10 per share ($110), and set aside $4,500. Ignoring costs, the table shows the result at expiration next to simply buying 100 shares at $50 today.
| Stock at expiration | What happens | Short put P/L | Buy 100 shares at $50 instead |
|---|---|---|---|
| $55.00 | Put expires worthless | +$110 | +$500 |
| $50.00 | Put expires worthless | +$110 | $0 |
| $45.00 | At the strike; no intrinsic value | +$110 | -$500 |
| $43.90 | Assigned; breakeven | $0 | -$610 |
| $40.00 | Assigned at $45 | -$390 | -$1,000 |
| $35.00 | Assigned at $45 | -$890 | -$1,500 |
| $30.00 | Assigned at $45 | -$1,390 | -$2,000 |
| $0.00 | Assigned at $45; shares worthless | -$4,390 | -$5,000 |
Three formulas come straight from the table:
- Breakeven = strike - premium = $45.00 - $1.10 = $43.90.
- Maximum gain = premium x 100 = $110, kept if the stock stays above the strike.
- Maximum loss = (strike - premium) x 100 = $43.90 x 100 = $4,390, if the stock goes to zero.
The best case is $110; the worst case, $4,390, is about 40 times larger. The $110 is roughly 2.4% on the $4,500 tied up, which sounds tidy until you remember what it pays for. If the stock rallies to $55, the put seller still makes only $110 while a shareholder makes $500. Gains stop at the premium; losses keep going down to the strike minus the premium.
Assignment, including early assignment
US equity options are generally American-style, meaning the holder can exercise on any business day before expiration. A short put can therefore be assigned at any time while it is open, not only at expiration. When a holder exercises, the Options Clearing Corporation (OCC) assigns the exercise notice at random among clearing firms with short positions in that series, and your firm then allocates it to one of its customers, either randomly or by another method it discloses. Ask your firm which method it uses.
Most exercises happen on or near expiration, but early assignment does occur. The Options Industry Council notes that when puts become deep in-the-money, most professional traders exercise them before expiration, so a seller of a deep in-the-money put should be prepared to be assigned early. Mergers, takeovers, spin-offs and special dividends can upset normal expectations.
You usually find out after the fact, and the stock can keep moving before you can react. If the secured cash sits in something interest-bearing, it must be available to pay for shares on short notice. If the put is in the money near expiration, plan on being assigned. If you do not want the shares on a given day, the only reliable way to avoid assignment is to buy the put back before that day's close.
A cash-secured put and a covered call: the same shape
If you have read covered calls, risk first, the payoff table above should look familiar. A covered call (own 100 shares, sell a call) and a cash-secured put (hold cash, sell a put) have the same basic shape: a small, capped gain if the stock rises, and almost all of the stock's downside if it falls. The OIC describes their risk profiles as essentially the same.
The reason is put-call parity, which in plain terms says: owning the stock and selling a call at a given strike behaves very much like holding cash equal to that strike and selling a put at the same strike and expiry. In both cases you end up owning the stock if it finishes below the strike, and your result is capped at a fixed amount if it finishes above. Option prices stay close to this relationship, after allowing for interest and expected dividends.
The differences are practical, not structural: the shareholder receives dividends while the put seller earns any interest on the cash; the trade counts and costs differ; and early assignment tends to happen for different reasons (dividends for calls, deep in-the-money moves for puts). Neither one is the "safer" version.
Choosing the strike and expiry
| Choice | You get | You give up |
|---|---|---|
| Strike closer to the stock price | More premium | Higher chance of assignment; a higher purchase price if assigned |
| Strike further below the stock price | A lower purchase price if assigned | Less premium, so less cushion per dollar of cash tied up |
| Shorter expiry | More frequent decisions, cash freed sooner | Less premium per trade; more trades and more costs |
| Longer expiry | More premium per contract | Cash committed for longer; more events (earnings, news) inside the window |
The decision rule that matters most: choose the strike as the price at which you would genuinely be happy to buy, at this size, today. The premium is secondary. If you would not place a limit order to buy the stock at $45, do not sell the $45 put.
Gap risk and earnings
A stop-loss does not protect a short put from a gap. Illustrative example: you sell the $45 put, earnings are released after the close, and the stock opens at $35. The put is now $10 in the money. Bought back or assigned, that is roughly an $890 loss on one contract, and there was no price between $45 and $35 at which you could have acted.
High premiums before an earnings report usually reflect a larger expected move. Treat them as a warning, not a bonus. Check the earnings date and decide in advance whether you will hold through it.
Costs
- Commissions and contract fees on the sale, any buyback or roll, plus any assignment fee your firm charges, and stock commissions when you later sell assigned shares.
- Bid-ask spread. In thinly traded options the spread can be a large share of a small premium. Use limit orders.
- Taxes. Premiums, assignment and closing trades can each have tax consequences that depend on your country and account type. This is general information only; rules change, so check with a qualified tax professional about your situation.
Illustrative example: if commissions, fees and spread total $10 on the $110 premium, your effective premium is $1.00 per share and your breakeven rises to $44.00. Record the net figures in your trade journal, not the headline premium.
Pre-trade checklist
- Would I buy 100 shares of this stock per contract at the strike price today, with no option involved? If not, stop.
- Is the full strike x 100 x contracts in cash in this account, not borrowed and not needed for anything else?
- Would that share position fit my normal sizing rules? (See position sizing with 1R: size by the loss you can take, not by the premium.)
- Have I written down breakeven, maximum gain and maximum loss in dollars, after costs?
- Is there an earnings report, ex-dividend date or corporate action before expiry?
- Is the option liquid enough to buy back at a fair price if I change my mind?
- If I am assigned and the stock keeps falling, what is my plan for the shares: hold, set a stop, or sell? Decide now.
Common mistakes
- Selling puts on stocks you would not own. High premiums usually mean high expected movement, and assignment makes that your problem.
- Sizing by premium. Selling five contracts because $550 looks better than $110, without noticing that the worst case just became $21,950 and the cash commitment $22,500.
- Using margin so it is no longer cash-secured. Selling more puts than your cash covers turns the trade into an uncovered (naked) put on margin. A sharp fall can then bring margin calls and forced liquidation at the worst prices.
Sources and further reading
Mechanics in this guide follow the Options Industry Council's cash-secured put strategy page, its pages on exercising options and understanding assignment, FINRA's trading options: understanding assignment, the SEC's introduction to options bulletin, and the OCC's equity options product specifications (check the live page for current terms). Canadian-listed options have their own specifications. More guides: the options topic page and market news. All numbers above are illustrative and are not a recommendation to trade any security.
Examples use round, illustrative numbers and are not actual trades or results. Education only — not investment, tax or legal advice.
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