A cash-secured put is a neutral-to-bullish options strategy where you sell a put contract and set aside cash collateral equal to 100 shares × strike price. You collect the premium upfront. If the stock stays above the strike, the put expires worthless and you keep the premium. If the stock falls below, you are obligated to buy 100 shares per contract at the strike price.
Mechanics, delta selection, annualized ROC, effective cost basis, and assignment management — with worked examples.
A cash-secured put (CSP) is the income strategy for anyone who wants to buy a stock at a discount — and is willing to wait. You set aside cash equal to 100 shares times your chosen strike. You sell someone the right to make you buy at that strike. They pay you premium up front. If the stock stays above the strike, you keep the premium. If it drops below, you buy the shares at the strike — exactly what you wanted to do anyway, just at a price below where you started.
Done on names you genuinely want to own, the CSP exchanges limited premium income for real assignment exposure — the trade-off is often favorable in flat-to-mildly-bullish markets on liquid large-caps, but historical risk-adjusted performance varies substantially by underlying, valuation, volatility regime, strike selection, and execution cost. Done on names you don't want to own, it's a recipe for catching falling knives. This guide separates the technique from the temptation.
Cash-secured put payoff at expiration
Stock onlyCash-Secured Put
Dashed gray line is the stock-only baseline (no option). The colored line is the strategy payoff at expiration. Green-tinted area is profit, red-tinted is loss.
How a cash-secured put works
The trade has three legs:
Set aside cash = strike × 100 × contracts. This is your maximum obligation.
Sell a put option at the chosen strike, below the current price. You receive premium up front.
Wait for expiration.
Three outcomes:
Stock stays above the strike → put expires worthless. You keep the premium and the cash. You can sell another put.
Stock closes below the strike → the put is exercised against you. You buy 100 shares at the strike. Effective cost basis = strike − premium.
Stock drops well below the strike → you still buy at the strike, taking an unrealized loss equal to (strike − market price) per share, partially offset by the premium received.
The premium received is yours regardless of outcome. The trade is “cash-secured” because the cash backing the put obligation is held aside — you can't spend it elsewhere until the put expires or is closed.
How to choose the strike
The key question is: at what price would I genuinely want to own this stock? Not “what looks like a good yield” — what price would make me happy to be a long-term owner. Sell the put at that strike (or slightly higher, accounting for the premium you'll receive).
Delta-based heuristics:
−0.15 delta — deep OTM. ~85% probability of expiring worthless. Low premium, low assignment risk. Used by traders who really don't want assignment.
−0.20 to −0.30 delta — the income-seller sweet spot. ~70–80% expire worthless. Reasonable premium.
−0.35 to −0.40 delta — close to spot. Rich premium, but ~40% chance of assignment. Used when you'd be happy to own at this price.
Avoid: selling CSPs on stocks you wouldn't own at the strike. Premium yield can lure you into bad positions. The wheel strategy works because the underlying selection is good, not because the math is clever.
Annualized return on capital
CSPs are measured in annualized return on capital (ROC), not just premium yield. The formula:
Annualized ROC = (Premium ÷ Cash secured) × (365 ÷ Days to expiration)
Example: SPY is at $756. You sell a one $750 put contract with 21 DTE for $3.40 per share (= $340 per contract, since one contract controls 100 shares). Cash secured = $75,000 per contract (100 shares × $750 strike). Annualized ROC = ($340 per contract ÷ $75,000 collateral) × (365 ÷ 21 days) = 7.9%. Equivalently, using per-share values: ($3.40 ÷ $750 strike) × (365 ÷ 21) = 7.9%. Both forms give the same answer because premium and collateral scale together by the 100-share multiplier.
That sounds modest, but consider: it's earned on cash that's just sitting there. As of the last static example update, a money-market fund yielded roughly 4-5% depending on the rate cycle; the current risk-free rate is dynamic and should be checked against your broker's cash sweep. If yours pays 4.5%, this CSP adds roughly 3.4% of incremental return. Over a year, repeated cycles add up.
Compare ROC across opportunities of different durations using the annualized number. A 14-day CSP earning 0.4% has the same annualized ROC as a 30-day CSP earning 0.86%.
Effective cost basis if assigned
The cost basis number tells you the “true” price you pay if assigned:
Effective cost basis = Strike − Premium received
Example: SPY at $756. You sell a $750 put for $3.40. If assigned, your effective cost basis is $746.60 — 1.2% below the current market price. You've essentially bought SPY at a discount by collecting premium for the obligation.
This is the right number to compare against the stock's fundamentals. “Would I buy SPY at $746.60?” is a much better question than “Should I sell a $750 put?”
For wheel-strategy traders, the effective cost basis becomes your new tracking number. You sell covered calls above this basis to ensure that any “called away” outcome is a profit.
What happens at assignment
If your CSP is assigned, the mechanics are straightforward:
The morning after expiration (or earlier if exercised early — uncommon for puts), you wake up to find 100 shares per contract in your account at the strike price.
The cash you'd set aside is debited and used to buy the shares.
The premium you received remains in your account.
At this point you have three reasonable choices:
Hold the shares. You wanted to own them; now you do. Sell covered calls against them for additional income (this is the wheel).
Sell the shares. If the stock has dropped further, you can take the loss and move on. The premium received reduces the loss.
Roll the put before expiration. Close the current short put and open a new one at a lower strike or later expiration, ideally for a net credit. This delays assignment if the stock has gone against you.
The right choice depends on whether your view of the underlying has changed. If the reason you wanted to own it still holds, hold. If it doesn't, sell.
CSPs and the wheel strategy
The cash-secured put is leg 1 of the wheel strategy:
Sell a CSP on a stock you'd happily own.
If assigned, you now own shares at an effective cost basis below current market.
Sell a covered call above your effective cost basis. Collect more premium.
If called away, you sell the shares at a profit and start over with another CSP.
If the call expires worthless, sell another covered call. Repeat until called away.
The wheel works because each leg compounds: you collect premium from the CSP, then more premium from the CC, then realize a small gain when called away, then start over. Annualized returns of 15–25% are achievable on liquid US large-caps in normal market regimes.
The wheel's weakness is sustained downtrends: being short puts forces purchases at falling prices. Stock selection is everything.
Frequently asked questions
How is annualized return on capital calculated for a CSP?
What's the effective cost basis if my CSP is assigned?
Effective cost basis = strike − premium received. That's the true price you'd pay per share if assigned — usually below the strike and often below the current market price.
What delta should I sell cash-secured puts at?
Income sellers typically target −0.15 to −0.30 delta, giving roughly a 70–85% chance the put expires worthless. Lower (more negative) deltas yield more premium but increase assignment risk.
Can I sell CSPs in a Roth IRA?
Yes, most brokers allow CSPs in Roth IRAs at the basic options-approval level. The cash backing the put must be in the same account. Naked puts (without the cash) are typically not allowed in IRAs.
Are cash-secured puts safer than buying the stock?
Slightly. The premium received cushions a small portion of downside. But the maximum loss is still substantial — equal to (strike − premium) × 100 if the stock goes to zero. CSPs are not a substitute for sound underlying selection.
Read more in this series
Deep dives into specific aspects of cash-secured-put selling.