Bull Put Spread — Bullish Credit Spread Với Probability Cao

Bull Put Spread (còn gọi là "Short Put Vertical" hoặc "Credit Put Spread") là một trong những chiến lược được traders chuyên nghiệp dùng nhiều nhất. Lý do: xác suất thắng cao, defined risk, và income liên tục từ theta decay.

Nếu Long Call và Bull Call Spread là "đặt cược stock tăng," Bull Put Spread là "đặt cược stock không giảm." Nghe đơn giản, nhưng khác biệt quan trọng: bạn có thể lời ngay cả khi stock đi ngang hoặc tăng nhẹ — không cần phải đúng về hướng, chỉ cần tránh sai nhiều.

Tóm Tắt Nhanh

Bull Put Spread Là Gì?

Bull Put Spread là strategy 2-leg credit spread:

1. SELL 1 Put tại strike higher (thường OTM, gần giá hiện tại)
2. BUY 1 Put tại strike lower (thường OTM xa hơn, as protection)

Cả 2 puts cùng expiration.

Bạn nhận net credit (premium short put - premium long put). Credit này là max profit. Max loss = spread width - credit.

Logic: Stock ở trên short strike → both puts expire worthless → bạn giữ credit = max profit. Stock về giữa strikes → partial profit hoặc loss. Stock dưới long strike → max loss, nhưng capped.

Cấu Trúc Lệnh

Leg 1: SELL 1 Put (short leg)
       Strike: Higher (OTM, close to current)
       
Leg 2: BUY 1 Put (long leg)
       Strike: Lower (further OTM, protection)
       
Both: Same expiration, same stock
Result: Net credit

Ví dụ:

Stock: SPY @ $585
Bull put spread (35 DTE):
  SELL 1 SPY 575 Put @ $3.50
  BUY 1 SPY 570 Put @ $2.20
  
Net credit: $3.50 - $2.20 = $1.30
Credit received: $130 per spread
Spread width: $575 - $570 = $5
Max profit: $130 (credit)
Max loss: ($5 - $1.30) × 100 = $370
Collateral required: $370

Khi Nào Dùng Bull Put Spread?

Use Case 1 — High Probability Income

Bán OTM puts = high probability of expiring worthless. Consistent income strategy for neutral-bullish markets.

Use Case 2 — High IV Environment

VIX cao → put premiums cao → larger credit collected. Sell premium khi IV expensive.

Use Case 3 — Support Level Trading

Stock ở key support level. Bạn tin support sẽ hold. Bán put spread với short strike tại hoặc dưới support.

Use Case 4 — Earnings Play (với Caution)

Before earnings với IV cao, credit spread cho vega harvest. Nhưng watch out cho earnings gap risk.

Khi KHÔNG Nên Dùng

• Strongly bearish market — high probability of reaching short strike
• Low IV — credit quá nhỏ, risk/reward không đáng
• Black swan event risk — gap down có thể trigger max loss
• Illiquid underlying — slippage ăn credit

Ví Dụ Thực Tế Chi Tiết

Scenario: SPY ở $585, you're neutral-to-bullish, expect SPY to stay above $575 over next month.

Setup:
Stock: SPY @ $585
Thesis: Hold above $575 (bullish bias)
Timeframe: 35 days

Trade:
SELL 1 SPY 575 Put (35 DTE) @ $4.00
BUY 1 SPY 570 Put (35 DTE) @ $2.50

Net credit: $4.00 - $2.50 = $1.50
Credit received: $150
Spread width: $5
Max profit: $150
Max loss: ($5 - $1.50) × 100 = $350
Collateral: $350

Probability of profit (delta 575 ~0.30): ~70%
R/R: $150 profit / $350 risk = 0.43:1

4 Outcomes Tại Expiration

Outcome 1 — SPY @ $590 (Max Profit)

Both puts OTM, expire worthless
Credit kept: $150
Profit: $150 (+43% on collateral)

Occurs at any price ≥ $575.

Outcome 2 — SPY @ $577 (Still Profitable)

Short 575 Put: OTM, worthless
Long 570 Put: OTM, worthless
Credit kept: $150
Profit: $150

Same as max profit, as long as SPY ≥ short strike.

Outcome 3 — SPY @ $573 (Partial Loss)

Short 575 Put: ITM by $2
  Intrinsic value: $200 (you owe)
Long 570 Put: OTM
  Intrinsic value: $0
Net cost to close: $200
Credit collected: $150
Net loss: $200 - $150 = -$50

Outcome 4 — SPY @ $565 (Max Loss)

Short 575 Put: $10 intrinsic
Long 570 Put: $5 intrinsic
Net value: $10 - $5 = $5 per spread
Cost to close: $500
Credit collected: $150
Net loss: $500 - $150 = -$350

Max loss at any price ≤ $570.

Max Profit / Max Loss / Breakeven

Max Profit:

Max Profit = Net Credit × 100

Với SPY example:

Max Profit = $150

Achieved when stock ≥ short strike ($575).

Max Loss:

Max Loss = (Width - Net Credit) × 100

Với SPY:

Max Loss = ($5 - $1.50) × 100 = $350

Occurs when stock ≤ long strike ($570).

Breakeven:

Breakeven = Short Strike - Net Credit per share

Với SPY:

Breakeven = $575 - $1.50 = $573.50

Greeks Behavior

Delta — Dương Nhỏ

• Short put: delta dương (~+0.30)
• Long put: delta âm (~-0.20)
• Net delta: +0.10

Position slightly bullish, much less directional than long stock.

Theta — Dương!

• Short put: theta dương (large)
• Long put: theta âm (smaller)
• Net theta: dương

Thời gian làm việc cho bạn. Đây là điểm mạnh chính của credit spreads.

Vega — Âm

• Short put: vega âm
• Long put: vega dương (smaller)
• Net vega: âm

IV giảm → profit. IV tăng → loss (nhưng capped). Tốt nhất khi bán in high IV environment.

Gamma — Âm

Stock di chuyển mạnh → gamma hurts you non-linearly. Short options always have gamma risk.

Ưu Điểm

• High win rate (65-80% cho OTM spreads)
• Defined risk — biết max loss trước
• Theta positive — time works in your favor
• Capital efficient — collateral = spread width (not full strike)
• IV premium capture — lời khi IV giảm
• Easy to manage — one decision point (close or let expire)

Nhược Điểm

• Asymmetric R/R — risk > reward
• Gap risk — overnight gap can cause max loss quickly
• Need many wins — small wins, one big loss can erase months
• Not for low IV — credit too small to justify risk
• Assignment risk — short leg can be assigned early (esp. before dividend)

Lỗi Người Mới Hay Mắc

Lỗi 1 — Ignore R/R Asymmetry

"Win rate 80% is great!" Yes, until 1 loss wipes 2-3 months of wins. Math: 80% × $150 wins - 20% × $350 losses = $120 - $70 = $50 avg per trade. Need consistency.

Fix: Understand the asymmetry. Position size accordingly. Don't risk more than 1-2% account per spread.

Lỗi 2 — Hold Đến Max Loss

Stock breaks support, spread at -50%. You hold "waiting for bounce." It breaks more, you hit max loss.

Fix: Stop at 1.5-2x credit loss. Ví dụ credit $150 → stop at -$225 to -$300 loss. Don't wait for max.

Lỗi 3 — Too Close To The Money

Selling 5-delta puts for "safe income." Max profit tiny, max loss huge. R/R terrible.

Fix: Target 15-30 delta for short strike. Balance of premium vs risk.

Lỗi 4 — Credit Spread Trên Stock Giảm

Stock đang downtrend, bạn bán put spread "at support." Support breaks, you take max loss.

Fix: Never sell put credit spreads in strong downtrends. Wait for stabilization or uptrend resumption.

Lỗi 5 — Earnings Gamble

Selling credit spread before earnings to capture high IV. Earnings miss, stock gaps down through both strikes, max loss overnight.

Fix: Either close before earnings or accept the gamble with small position. Don't pretend it's "safe income."

Exit Management

Scenario 1 — Profit Taking

At 50% of max profit → close (best R/R exit). At 75% → definitely close.

Scenario 2 — Losing Trade

If spread approaches -1.5x credit → close to avoid max loss.

Scenario 3 — Stock Near Short Strike

Delta của short put > 0.50 → consider rolling or closing. Don't let it approach max loss slowly.

Scenario 4 — Wait to Expire

Only for deep OTM spreads at very low extrinsic value. Commission vs extrinsic trade-off.

The 50% Rule

Rule: Close credit spreads at 50% of max profit.

Why: Math shows the first 50% comes easily (theta acceleration), the last 50% has worst R/R (days of risk for small additional profit).

Example:

Credit: $150
Target: $75 profit (50% of max)
At $75 profit: close position, redeploy capital

Đây là một trong những best practices universal cho credit spreads.

Pre-Trade Checklist

☐ Neutral-bullish thesis?
☐ Support level identified?
☐ IV decent (not too low)?
☐ Short strike OTM enough (15-30 delta)?
☐ Width appropriate for account size?
☐ Max loss ≤ 2% account?
☐ Exit plan defined (50% profit target)?
☐ Not selling over earnings?

Chiến Lược Liên Quan

• Cash-Secured Put — Similar but requires full collateral
• Bear Call Spread — Bearish credit spread
• Iron Condor — Combine bull put + bear call

Học Credit Spreads Với Dan Steel

Credit spreads là backbone của nhiều professional traders' income strategies. Dan Steel dạy cách chọn strikes, size positions, và manage losses.

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