Choosing a Strike and Expiration for a Cash-Secured Put
When you sell a cash-secured put, the strike you pick is the price you agree to pay for the shares if you are assigned, and the premium you collect is the price the buyer pays you for that promise. The expiration date sets how long the promise lasts. Those two choices decide both how much you are paid and how likely you are to end up owning the stock, so they are worth understanding before you place the trade.
This page covers the strike and expiration for a cash-secured put only. The same two decisions on a covered call run the opposite direction, and they are a separate decision on shares you already hold, so they live on choosing a strike for a covered call. The two are independent income decisions, judged on their own merits, not a loop run on one ticker.
The precondition: a strike you would accept
Section titled “The precondition: a strike you would accept”A cash-secured put obligates you to buy 100 shares at the strike if the stock is below it at expiration, with cash you have set aside to cover that purchase. So the strike is not a number you reach for because the premium looks good. It is a price you would genuinely be content to pay for shares you would be happy to own. Pick the strike first as a buyer, then look at what the premium pays you for waiting. If you would not want to own the stock at that price, no premium makes the trade worth selling.
How the strike sets your price and your premium
Section titled “How the strike sets your price and your premium”The strike does two things at once.
It sets your effective purchase price. If you are assigned, you pay the strike, but the premium you already collected reduces what the shares actually cost you. Sell a put with a $160 strike and collect $2.00 per share, and your effective cost if assigned is $158 a share. The premium is yours either way, so it always lowers your basis when you do end up buying.
It sets your premium and your assignment odds together, and the two move in opposite directions. A strike close to the current price pays more, because the stock has a shorter distance to fall before the put finishes in the money. A strike well below the current price pays less, because the stock has to drop further before you are obligated to buy. You are trading premium for the buffer between today’s price and your strike.
| Strike relative to price | Premium collected | Chance you are assigned |
|---|---|---|
| Well below the current price | Lower | Lower |
| Slightly below the current price | Moderate | Moderate |
| At the current price | Higher | Roughly even |
Most cash-secured-put sellers work at or slightly below the current price, where the premium is reasonable and the strike is still one they would accept as a buyer. A strike at or above the current price pays the most but is the most likely to leave you owning shares, so it suits only a seller who wants the stock now and treats the premium as a discount on an entry they were going to make anyway.
Delta as a rough proxy for assignment
Section titled “Delta as a rough proxy for assignment”When you scan a put’s strikes, each one carries a delta, a number that, for an out-of-the-money put, works as a rough proxy for the chance the option finishes in the money and you are assigned. A delta near 0.30 points to roughly a 30% chance of finishing in the money. Many sellers starting out anchor on the 0.20 to 0.30 range, which keeps the strike well enough below the current price that assignment is the less likely outcome while the premium is still worth collecting.
Treat delta as a guide, not a measurement. It is the market’s running estimate, not a probability you can bank on, and it shifts as the stock moves and as volatility changes. Use it to compare strikes and to size up roughly where you are, not as a number that tells you what will happen. For where delta comes from and how it behaves, see the Greeks.
How expiration changes the trade
Section titled “How expiration changes the trade”A nearer expiration pays a smaller premium in absolute terms but decays faster per day, because an option loses its time value more quickly as expiration approaches. A further expiration pays more upfront but ties up your cash longer and leaves more time for the stock to move against you and fall through your strike. A 30-to-45-day expiration is a common middle ground: enough premium to be worth the trade, fast enough decay to work in your favor, and a planning rhythm you can check periodically rather than watch daily.
A longer expiration also raises your assignment odds at any given strike, since the stock has more time to reach it. So expiration and strike are not separable choices. Moving the expiration out is one more way of trading premium for a higher chance of ending up with the shares.
Before you settle on an expiration, check whether an earnings announcement falls inside it. Earnings can move a stock 10% or more in a single session, which inflates the premium because the risk is real. If you do not want that event risk, choose an expiration that lands before the announcement, or pick a different cycle.
A worked example
Section titled “A worked example”Say a stock you would be happy to own trades at $170, and you have already decided $160 is a price you would accept as a buyer. You set aside $16,000 in cash to cover 100 shares at that strike.
You sell a put with a $160 strike, 30 days out, and collect $2.00 per share, so $200 lands in your account immediately. The $160 strike sits about 6% below the current price, which is the buffer you are buying with a lower premium than an at-the-money strike would pay.
Two things can happen at expiration:
- The stock closes above $160. The put expires without assignment and you keep the $200. On the $16,000 you set aside, that is about 1.25% for the 30 days you held the cash at risk. What that works out to over a year depends on volatility, the strikes you choose, and whether every cycle even offers a strike you would accept, so it is a figure to judge for your own situation, not a rate to assume.
- The stock closes below $160. You are assigned and buy 100 shares at $160, for an effective cost of $158 a share once the premium is counted. That is the price you decided was fair before you sold. If the stock has fallen well below $160, you still own it at $158, which is the risk you accepted the moment you chose a strike you were willing to buy at. A limit order at $160 would have left you in the same position, minus the $200.
Both outcomes were acceptable before you sold, which is the test. If only one of them would have been, the strike was wrong.
Where to go next
Section titled “Where to go next”- How cash-secured puts work: the full mechanics of selling a put, collateral, and the three outcomes at expiration.
- The Greeks: where delta comes from and why it is a rough proxy, not a measurement.
- A cash-secured put, start to finish: one trade carried from setup through to its outcome.