Cash-secured puts: a complete guide

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 is one of the highest-Sharpe-ratio strategies available to retail traders. 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.

How a cash-secured put works

The trade has three legs:

1. Set aside cash = strike × 100 × contracts. This is your maximum obligation.
2. Sell a put option at the chosen strike, below the current price. You receive premium up front.
3. 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 $750 put with 21 DTE for $3.40 premium. Cash secured = $75,000. Annualized ROC = (3.40/75,000) × (365/21) = 7.9%.

That sounds modest, but consider: it's earned on cash that's just sitting there. If you'd otherwise have that money in a money-market fund earning 4.5%, the CSP adds 3.4% of incremental return. Over a year, repeated cycles add up significantly.

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:

1. 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.
2. The cash you'd set aside is debited and used to buy the shares.
3. 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:

1. Sell a CSP on a stock you'd happily own.
2. If assigned, you now own shares at an effective cost basis below current market.
3. Sell a covered call above your effective cost basis. Collect more premium.
4. If called away, you sell the shares at a profit and start over with another CSP.
5. 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

Read more in this series

Deep dives into specific aspects of cash-secured-put selling.