Vertical Credit Spread (Bull Put / Bear Call)

The vertical credit spread is the workhorse defined-risk strategy of the systematic premium-selling approach. It sells an out-of-the-money (OTM) option and simultaneously buys a further-OTM option of the same type and expiration, collecting a net credit while capping the maximum loss at the width of the strikes. It is directional-to-neutral, capital-efficient, and — critically — it is the building block from which the iron condor is assembled. This entry treats the bull put spread (short put vertical) and the bear call spread (short call vertical) together, because they are mirror images: identical mechanics, opposite directional bias.

---

1. Overview & Purpose

A vertical credit spread is a two-leg, single-expiration position in which you sell an option near the money and buy a cheaper option further from the money to define your risk. The net premium is a credit that lands in your account at entry, and that credit is the most you can make.

The purpose is to express a directional-to-neutral thesis with known, capped risk while still being a net seller of premium. Like all short-premium structures, it profits from the passage of time (theta) and from the short option finishing out-of-the-money, but unlike a naked short option, its downside is fixed at order entry.

Bull put spread (short put vertical): sell the higher-strike put, buy the lower-strike put. Bullish-to-neutral — you profit if the underlying stays above the short put.
Bear call spread (short call vertical): sell the lower-strike call, buy the higher-strike call. Bearish-to-neutral — you profit if the underlying stays below the short call.

The strategy's appeal is its risk/reward symmetry and accessibility: it is permitted in IRAs and in margin accounts, requires far less buying power than a naked short option, and lets a small account participate in premium selling without unbounded tail risk.

---

2. Structure & Payoff

Legs (bull put spread, bullish-to-neutral):

1. Sell to open 1 put at the higher strike (near ~30 delta, just OTM).

2. Buy to open 1 put at a lower strike (further OTM, same expiration) to define risk.

Legs (bear call spread, bearish-to-neutral):

1. Sell to open 1 call at the lower strike (near ~30 delta, just OTM).

2. Buy to open 1 call at a higher strike (further OTM, same expiration) to define risk.

The distance between the two strikes is the spread width. Net credit = premium received on the short leg − premium paid on the long leg.

ASCII payoff at expiration — Bull Put Spread (sell 40 put / buy 35 put for a $2.00 credit, width $5):

ASCII payoff at expiration — Bear Call Spread (sell 55 call / buy 60 call for a $1.50 credit, width $5):

Both structures have the same shape: a flat profit plateau capped at the credit, a sloped transition zone of width = the strike width, and a flat loss floor capped at (width − credit). The bull put plateau is to the right (price stays up), the bear call plateau is to the left (price stays down).

---

3. When to Use

You have a directional-to-neutral lean. Sell a put spread when you are bullish/neutral and a call spread when you are bearish/neutral; the spread profits across a wide band, not just on a precise forecast.
Implied volatility is elevated. Higher IV inflates the credit you collect for a given delta, widening the breakeven and improving reward-for-risk. The premium-selling playbook favors selling when IV Rank is elevated (commonly IVR ≥ 50).
You want defined risk / limited buying power. A credit spread caps the loss and the buying-power reduction at (width − credit), making it the natural choice in IRAs, small accounts, or on high-priced underlyings where a naked short would be capital-prohibitive.
You want a probability-of-profit edge. Because the credit shifts the breakeven away from the money, a properly placed credit spread starts with a POP above 50%.

---

4. When NOT to Use

When IV is very low. Low IV shrinks the credit, so you are paid little to assume the width of risk; the reward-for-risk degrades and the breakeven buffer is thin. Premium sellers prefer to wait for richer volatility.
When you have a strong, fast directional conviction. If you are confident in a large move, a debit spread (long vertical) or a long option offers better leverage to the move; a credit spread caps the upside at the credit. The premium-selling literature explicitly frames credit-vs-debit as a choice driven by IV and thesis.
Across a binary event you don't want exposure to (e.g., earnings) unless that is the explicit trade — gap risk can carry the underlying straight through both strikes to max loss.
When you cannot manage assignment/pin risk near expiration. A defined-risk spread "is no longer a defined risk position if one leg expires in the money and the other does not," creating after-hours assignment and pin risk. Close or roll before expiration.

---

5. Entry Criteria

IV environment: Prefer elevated IV. The systematic framework sells premium when IV Rank is high (commonly IVR ≥ 50), because the option is rich relative to its own one-year range and tends to mean-revert lower.
DTE: Target ~45 days to expiration, the entry sweet spot that balances theta income against gamma risk. See 05_trade_management for the full rationale.
Short-strike selection (delta): A common default is to place the short strike near ~30 delta — just OTM, giving roughly a 70% chance of finishing OTM — with the long leg one or more strikes further out. Recall that delta approximates the probability of finishing in-the-money: a ~16-delta strike sits near the 1-standard-deviation (84% OTM) point, a ~30-delta strike is closer to the money with a fatter credit.
Width / credit target — the "1/3 rule": A widely taught rule of thumb is to collect roughly one-third of the width of the strikes, which corresponds to about a 66% probability of profit. For a $5-wide spread that means targeting ~$1.65 of credit. Wider credits relative to width mean more reward but lower POP; thinner credits mean higher POP but less reward.
Sizing: Size by max loss, not by credit. Keep any single defined-risk position to a small fraction of net liquidating value so a max-loss outcome is survivable; see 06_portfolio_management for occurrence-based sizing.

---

6. Greeks Exposure

For a credit spread, the short leg dominates the net Greeks because it is closer to the money, but the long leg dampens every exposure relative to a naked short.

Delta: Net long (bull put) or net short (bear call), but modest. The long wing offsets part of the short leg's delta, so a credit spread is far less directional than the equivalent naked short.
Theta (positive): The position earns time decay each day the underlying stays on the right side of the short strike. Theta is the primary profit engine.
Gamma (negative, magnitude grows into expiration): Short-gamma exposure is small early but accelerates as expiration nears, which is why a small adverse move close to expiry can swing P/L sharply — see 05_trade_management on the 21-DTE gamma stop.
Vega (negative): The net short option makes the spread short vega — though the long wing reduces the vega magnitude versus a naked short, so a credit spread is less sensitive to an IV spike than an undefined short.

---

7. Volatility Exposure

A vertical credit spread is net short vega: you sold more extrinsic value than you bought, so rising implied volatility inflates the spread's value (a mark-to-market loss) and falling IV deflates it (a gain), holding price constant.

IV expansion (bad, but buffered): If IV rises, the short option gains value faster than the long, hurting open P/L. However, the long wing caps how much that vega exposure can compound — a key advantage over a naked short during a volatility spike.
IV contraction (good): A drop in IV is a tailwind. Because credit sellers prefer to enter when IV is already elevated (high IV Rank), they position for mean reversion: the most common path is IV grinding back down, which helps the position even before time decay.
Net vega is smaller in magnitude than the equivalent undefined short, so the strategy is the defined-risk way to be short volatility.

---

8. Expected Behavior

P/L drivers. Three forces move a credit spread: direction (delta), time (theta), and volatility (vega). The base case is favorable — as long as the underlying stays on the right side of the short strike, theta bleeds the spread's value toward zero and you keep the credit.

Max profit = net credit received. Realized when the entire spread expires OTM (price at/above the short put, or at/below the short call). "The max profit you can make on a credit spread is the credit collected — you can't make anything more than you sold it for."

Max loss = (width − credit) × 100. Realized when the spread finishes fully in-the-money (both strikes breached). For a $5-wide put spread sold for $2.00: ($5 − $2) × 100 = $300.

Breakevens (one per spread, at expiration):

Bull put: short put strike − credit (e.g., 40 − 2 = 38).
Bear call: short call strike + credit (e.g., 55 + 1.50 = 56.50).

Probability of profit. POP is "the chance of making at least \$0.01 on a trade," and selling premium raises it: the credit pushes the breakeven away from the current price, so "the stock price can stay the same, go in our favor, or go against us just a bit and we'll still be profitable." A useful approximation for a credit spread is POP ≈ 1 − (credit ÷ width) — collecting one-third of the width implies roughly a 66% POP. There is a structural trade-off: collecting a bigger credit raises max profit and return-on-capital but lowers POP, and vice versa. See 02_probability for the full POP framework.

---

9. Capital Requirements / Buying Power

The buying-power reduction for a credit spread equals its maximum loss: (width − credit) × 100. For the $5-wide put spread sold at $2.00, the requirement is $300; for the $5-wide call spread sold at $1.50, it is $350.

This is dramatically more capital-efficient than the equivalent naked short, whose buying power scales with the underlying's notional value and whose risk is theoretically unbounded (short call) or very large (short put). Because the max loss is known and bounded, credit spreads are permitted in IRAs as well as margin accounts. Return-on-capital is computed against this fixed requirement, which makes credit spreads easy to size and compare across underlyings; see 06_portfolio_management.

---

10. Adjustment Criteria

Credit spreads are less adjustable than undefined-risk trades — the long wing fixes your risk, but it also limits how much you can roll for a credit or re-center without buying back the spread. Experienced premium sellers are explicit that defined-risk structures have fewer good defensive moves than strangles.

Roll out in time (same strikes, later cycle): When the tested side is under pressure and you still want exposure, roll the whole spread to the next expiration for a net credit, resetting duration and reducing gamma. Only roll if it can be done for a credit and improves probabilities.
Roll the spread away (out and down/up): Roll the strikes further from the money in a later cycle to widen the breakeven, again only for a credit.
Add the opposite-side credit spread → become an iron condor. A classic defense on a tested single spread is to sell a credit spread on the other side, collecting more premium and creating a neutral iron condor. This "defends the untested side" by bringing in credit that offsets the loss on the tested side.
Inverting (rolling the tested side past the untested side) is a strangle/condor-management tactic and is generally constrained or impractical on a simple defined-risk vertical.

Limitation to state plainly: a credit spread's defenses mostly require adding duration or adding a second spread; you cannot endlessly roll for credits the way you can with undefined trades. Often the cleanest "adjustment" is simply taking the defined loss.

---

11. Exit Criteria

Profit target — ~50% of max profit. The standard default for short premium, including defined-risk spreads, is to take winners near 50% of the credit collected. For a spread sold at $2.00, buy it back near $1.00.
Time stop — manage near 21 DTE. Close or roll as the position approaches ~21 days to expiration, regardless of P/L, to escape accelerating gamma risk. This is the same gamma-driven rule applied to all short premium; see 05_trade_management.
Defense / stop: With a known max loss, a hard percentage stop matters less than on undefined trades, but discipline still applies — exit or roll before the spread rides to its full capped loss rather than holding a near-certain loser into expiration.
Always close/roll before expiration if one leg is ITM to avoid pin risk and after-hours assignment turning a defined-risk spread into an undefined stock position.

---

12. Historical Research Findings

Managing winners at ~50% of max profit (applies to defined-risk spreads). A widely cited winner-management study — selling SPY 1SD short premium and exiting at stepped profit targets — found ~50% of max profit the best balance of P/L-per-day, win rate, duration, and drawdown versus holding to expiration; the same ~50% target is applied to defined-risk spreads and iron condors.
Initiating & managing credit spreads. A dedicated research segment addressed strike placement and management for credit verticals specifically, reinforcing the ~30-delta short strike and ~50% management approach. (Episode page returns 404 to automated fetching; results are reported from third-party search summaries and tagged accordingly.)
The "1/3 of width → ~66% POP" rule. Industry research popularized the heuristic that collecting one-third of the strike width on a credit spread corresponds to roughly a 66% probability of profit — a fast way to balance credit against POP at entry.
Credit vs. debit spread selection. Multiple research segments compared credit and debit verticals, framing the choice around the IV environment and directional conviction rather than one being universally superior.
IV-Rank-based profit targets. Later research explored scaling the profit target by IV Rank (bank faster in low IV, hold longer in high IV), suggesting ~50% is a robust default rather than the only defensible number.

Sourcing caveat: several of these industry pages return 404 to automated fetching, so the quantitative claims drawn from them are reported from third-party search summaries, tagged Conf Med, and not verbatim-confirmed. The two `/learn/` strategy pages (short put vertical, short call vertical) were fetched directly and their formulas and examples verified. No URL here is fabricated.

---

13. Worked Example

Bull put spread on XYZ at \$45, elevated IV, ~45 DTE.

Sell the 40 put @ \$4.00 (short strike just OTM, ~30 delta).
Buy the 35 put @ \$2.00 (long wing, defines risk).
Net credit: \$4.00 − \$2.00 = \$2.00 ( = \$200 per spread).
Spread width: 40 − 35 = \$5.
Max profit: the credit = +\$200 (XYZ ≥ 40 at expiration).
Max loss: (width − credit) × 100 = (\$5 − \$2) × 100 = −\$300 (XYZ ≤ 35 at expiration).
Breakeven: short strike − credit = 40 − 2 = \$38.
Buying-power reduction: = max loss = \$300.
Profit target: ~50% of \$200 → buy the spread back near \$1.00 for a +\$100 gain.

Outcome scenarios at expiration:

A bear call spread is the exact mirror: with XYZ at \$50, sell the 55 call @ \$3.00 / buy the 60 call @ \$1.50 for a \$1.50 credit on a \$5 width → max profit +\$150 (XYZ ≤ 55), max loss −\$350 (XYZ ≥ 60), breakeven 55 + 1.50 = \$56.50, buying power \$350.

---

14. Key Takeaways

A credit spread sells a near-the-money option and buys a further-OTM option of the same type/expiration for a net credit; bull put = sell higher put / buy lower put (bullish-neutral), bear call = sell lower call / buy higher call (bearish-neutral).
Max profit = credit; max loss = (width − credit); breakeven = short strike ∓ credit. Risk and reward are fully known at entry.
The credit raises POP above 50% by buffering the breakeven; the "collect ~1/3 of the width" heuristic targets ~66% POP.
Enter in elevated IV (high IV Rank), ~45 DTE, short strike ~30 delta.
Net short vega, positive theta, modest directional delta, negative gamma that bites near expiration.
Manage winners ~50% of max profit; close or roll near 21 DTE; always neutralize ITM legs before expiration to avoid assignment/pin risk.
Capital-efficient and IRA-eligible (buying power = max loss), and the building block of the iron condor — two opposing credit spreads.
Limited adjustability vs. undefined trades: defenses mainly add time or add the opposite spread; sometimes the right move is to take the capped loss.

---

Sources

options education — Short Put Vertical Spread Options Strategy Explained (fetched & verified) — https://www.theocc.com/company-information/documents-and-archives/options-disclosure-document
options education — Short Call Vertical Spread Options Strategy Explained (fetched & verified) — https://www.theocc.com/company-information/documents-and-archives/options-disclosure-document
options education — Iron Condor Strategy Guide — https://www.theocc.com/company-information/documents-and-archives/options-disclosure-document
this approach — Probability of Profit (POP) When Trading Options (fetched & verified) — https://www.theocc.com/company-information/documents-and-archives/options-disclosure-document
this approach — Options Delta Explained — https://www.theocc.com/company-information/documents-and-archives/options-disclosure-document
this approach — Options Vega: What Is Vega & How to Measure It — https://www.theocc.com/company-information/documents-and-archives/options-disclosure-document
this approach — Implied Volatility (IV) Rank & Percentile Explained — https://www.theocc.com/company-information/documents-and-archives/options-disclosure-document
industry research — Initiating & Managing Credit Spreads (2017-01-11) — https://www.theocc.com/company-information/documents-and-archives/options-disclosure-document
industry research — Managing Winners | Varying Profit Targets (2015-12-04) — https://www.theocc.com/company-information/documents-and-archives/options-disclosure-document
industry research — IV Rank Based Profit Targets (2019-11-06) — https://www.theocc.com/company-information/documents-and-archives/options-disclosure-document
industry research — Why Credit or Debit Spreads (2017-08-08) — https://www.theocc.com/company-information/documents-and-archives/options-disclosure-document
industry research — Defending Trades — Rolling to Increase Probabilities (2016-05-18) — https://www.theocc.com/company-information/documents-and-archives/options-disclosure-document
industry research — Credit and Debit Vertical Spreads (2015-09-30) — https://www.theocc.com/company-information/documents-and-archives/options-disclosure-document
broker education — Short (Credit) Vertical Spread — https://www.theocc.com/company-information/documents-and-archives/options-disclosure-document

Sourcing note: the two `/learn/` vertical-spread pages and the systematic-framework POP page were fetched directly and their formulas, examples, and phrasing verified. The show-episode pages are real, indexed source URLs surfaced via domain-restricted search; their quantitative results are reported from third-party search summaries (the episode pages return 404 to automated fetching) and are tagged Conf Med where not verbatim-confirmed. No URL is fabricated.

Related: 05_trade_management · 03_implied_volatility · 02_probability · 06_portfolio_management · 10_iron_condors

_Evidence-labeled per the Project Charter. Education only, not financial advice._