Options Trading Fundamentals

Credit Spreads

Q: What delta should the short leg have?

The most widespread reference is delta 0.16 to 0.30 on the short leg, roughly equivalent to a 70–84% chance of expiring worthless. Below 0.16 the credit collected is usually so small that commissions and a single loser eat several winners; above 0.30 probability drops enough that the unfavourable risk-reward stops being compensated. Delta 0.30 with high IV Rank is a reasonable starting point.

Q: How much credit should I demand for the spread width?

The most-used practical rule is collecting at least one third of the width: $1.65 or more on a $5 spread, $3.30 or more on a $10 one. If the market does not offer it, either implied volatility is too compressed to be worth selling, or you have placed your strikes too far out. In both cases the correct answer is not to do the trade, not to accept insufficient credit for risk that has not changed.

Q: What do I do if price breaks through my short strike?

It depends how much time remains. With more than 21 days, rolling to a later expiration for a net credit is usually the best option: you buy time and improve breakeven. With fewer than 21 days, gamma makes the position move too fast to manage well and closing to take the controlled loss is normally preferable. What almost never works is waiting and hoping it comes back: that is the decision that turns a manageable loss into the maximum one.

Q: Why does my credit spread lose value right after I open it?

Almost always the bid-ask spread. On entry you collect the market price but the position is valued at the mid or at the buyback price, which surfaces an immediate loss equal to the transaction cost. It is not a real loss until you close. The way to reduce it is trading underlyings with liquid chains and using limit orders near the mid rather than market orders.

ES: Spreads de Crédito PT: Spreads de Crédito

Structures that collect premium upfront and win if nothing happens: the mathematics of high probability and why it demands different management.

What a credit spread is

A credit spread is a structure in which the premium collected on the short legs exceeds the premium paid on the long ones, so money enters your account at entry. The two canonical cases are the bull put spread — sell the higher-strike put, buy the lower one — and the bear call spread — sell the lower-strike call, buy the higher one. The sold leg generates the income and defines where the trouble starts; the purchased leg exists solely to put a ceiling on that trouble. The credit received is your maximum gain, realised if both options expire worthless.

The inverted mathematics

The arithmetic is the mirror image of the debit. Maximum gain is the credit collected. Maximum loss is the strike width minus the credit. The breakeven is the sold strike minus the credit in a bull put spread, or the sold strike plus the credit in a bear call spread. With an example: with the stock at 100, you sell the 95 put for 1.80 and buy the 90 put for 0.60, collecting 1.20 of credit on a 5-wide spread. Maximum gain $120, maximum loss $380, breakeven 93.80. Note the asymmetry: you risk $380 to make $120, a little worse than 1-to-3 against you. What compensates that unfavourable ratio is probability: the trade wins in any scenario where the stock does not fall more than 6.2%.

Probability versus expectancy

Here lies the most expensive misunderstanding in premium selling. An 80% win probability sounds like certainty, but expectancy is only positive if the payoff compensates that distribution. With the example structure, winning $120 76% of the time and losing $380 24% of the time gives an expectancy of +$0.30 per trade before commissions: essentially zero. The real profitability of selling premium does not come from high probability alone, but from three things you must actively pursue: selling when IV is expensive relative to its own history, so the credit collected exceeds the statistical risk; closing before expiration so you do not carry the most dangerous part of the distribution; and never letting a loss reach the maximum. Without these three, a premium seller with an 80% win rate can finish the year negative without understanding why.

Time and volatility work in your favour

The structure carries positive theta: every day without an adverse move adds value, because the short leg’s extrinsic erodes faster than the long leg’s. And it carries negative vega: a compression in implied volatility makes the structure cheaper to buy back and produces profit even if price does not move. This double advantage is why premium selling is associated with the 30-to-45-day window: it is the zone where the decay curve accelerates noticeably while gamma — the acceleration of delta, which is what makes a position ungovernable near expiration — remains manageable. Entering at 60 days decays too slowly; entering at 7 days collects little and exposes you to disproportionate gamma risk.

Management: the part that decides the outcome

In credit structures, management matters more than selection. Three widely tested rules. First, close at 50% of the credit: if you collected 1.20 and can buy it back at 0.60, close. That 50% is typically reached in considerably less than half the time, so return per day of capital deployed is far higher than waiting for expiration, and it removes exposure to the final stretch where gamma risk lives. Second, manage the loss before the maximum: a common limit is closing when the loss reaches twice the credit collected. Third, roll only for a net credit: moving the structure to a later expiration makes sense if doing so collects more premium, because that improves breakeven; rolling for a debit is adding to a losing bet.

Frequently Asked Questions

What delta should the short leg have?

The most widespread reference is delta 0.16 to 0.30 on the short leg, roughly equivalent to a 70–84% chance of expiring worthless. Below 0.16 the credit collected is usually so small that commissions and a single loser eat several winners; above 0.30 probability drops enough that the unfavourable risk-reward stops being compensated. Delta 0.30 with high IV Rank is a reasonable starting point.

How much credit should I demand for the spread width?

The most-used practical rule is collecting at least one third of the width: $1.65 or more on a $5 spread, $3.30 or more on a $10 one. If the market does not offer it, either implied volatility is too compressed to be worth selling, or you have placed your strikes too far out. In both cases the correct answer is not to do the trade, not to accept insufficient credit for risk that has not changed.

What do I do if price breaks through my short strike?

It depends how much time remains. With more than 21 days, rolling to a later expiration for a net credit is usually the best option: you buy time and improve breakeven. With fewer than 21 days, gamma makes the position move too fast to manage well and closing to take the controlled loss is normally preferable. What almost never works is waiting and hoping it comes back: that is the decision that turns a manageable loss into the maximum one.

Is early assignment dangerous in a credit spread?

More inconvenient than dangerous, because the purchased leg still caps total risk. It happens almost always in two situations: deep in-the-money puts very close to expiration, and short calls the day before a dividend when their extrinsic value is less than the dividend. The result is a stock position and an immediate margin requirement. It is avoided by closing before expiration and checking the dividend calendar before selling calls.

Why does my credit spread lose value right after I open it?

Almost always the bid-ask spread. On entry you collect the market price but the position is valued at the mid or at the buyback price, which surfaces an immediate loss equal to the transaction cost. It is not a real loss until you close. The way to reduce it is trading underlyings with liquid chains and using limit orders near the mid rather than market orders.