When is it optimal to exercise an American call option early, and why do dividends matter?

Question

AcadiFi · Accepted Answer

This is a classic CFA Level II topic that tests whether you truly understand option value decomposition.

## Non-Dividend-Paying Stock: Never Exercise Early

An American call on a non-dividend stock is always worth more alive than dead. Here is why:

**If you exercise:** You receive S - K (intrinsic value).
**If you hold:** You keep the intrinsic value PLUS the time value PLUS the insurance value of downside protection.

By exercising early, you:
1. **Lose time value** — the possibility of the stock rising further
2. **Pay K now** instead of later — you lose interest on K for the remaining life
3. **Give up downside protection** — if the stock crashes after exercise, you bear the full loss

Since all three factors favor holding, early exercise is never optimal.

## Dividend-Paying Stock: May Exercise Just Before Ex-Date

When a stock goes ex-dividend, the price drops by approximately the dividend amount. If you hold the call through the ex-date, you suffer this price drop without receiving the dividend (only shareholders get dividends, not call holders).

**The tradeoff:**

| Exercise Early | Continue Holding |
|---|---|
| Receive stock, collect dividend | Keep time value |
| Give up remaining time value | Miss the dividend |
| Pay K now (lose interest) | Preserve optionality |

**It is optimal to exercise early when the dividend exceeds the time value remaining in the option.**

## Worked Example — Blackthorn Energy

Blackthorn declares a $3.00 per share dividend. Ex-date is tomorrow. You hold a call with K = $60, stock at $78.

**Option pricing (before ex-date):**
- Intrinsic: $78 - $60 = $18.00
- Premium: $18.80
- Time value: $18.80 - $18.00 = **$0.80**

**Decision:** The dividend ($3.00) far exceeds the time value ($0.80). If you do NOT exercise, you lose $3.00 in stock price drop and keep only $0.80 in time value. Net loss = $2.20.

**Therefore: exercise early** to capture the $3.00 dividend.

```mermaid
flowchart TD
    A{"Is dividend > time value?"}
    A -->|"Yes: Div $3.00 > TV $0.80"| B["Exercise Early
Capture Dividend"]
    A -->|"No: Div < Time Value"| C["Hold Option
Keep Optionality"]
    style B fill:#2d6a4f,color:#fff
    style C fill:#1a5276,color:#fff
```

## Key Rules

1. Early exercise is only considered just before ex-dividend dates, never at other times
2. Deep ITM calls with small time value are most likely candidates
3. American puts CAN be exercised early even without dividends (when deep ITM, the interest on K becomes valuable)

**Exam tip:** If a vignette mentions dividends and American calls, check whether the dividend exceeds time value. That determines whether early exercise is optimal.

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When is it optimal to exercise an American call option early, and why do dividends matter?

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