Defined Risk, Premium Income:
Credit Spreads Explained

What is a credit spread?

A credit spread is a two-leg options position where you sell one option and simultaneously buy another option of the same type (both calls or both puts), same expiry, but at a different strike price. Because the option you sell is closer to the money (and therefore more expensive) than the option you buy, the position collects a net premium at entry — hence "credit."

The long leg you buy serves as insurance: it caps your maximum loss to the width of the spread minus the credit received, while significantly reducing the margin requirement compared to a naked short option. This defined-risk profile makes credit spreads one of the most practical strategies for retail options traders on NSE.

Two types: bull put spread and bear call spread

Bull put spread (bullish or neutral outlook). You sell an OTM put at a higher strike and buy an OTM put at a lower strike. You collect a net credit. The spread profits if the underlying stays above your short put strike at expiry. Maximum profit equals the net premium received. Maximum loss equals the spread width minus the net credit.

Bear call spread (bearish or neutral outlook). You sell an OTM call at a lower strike and buy an OTM call at a higher strike. You again collect a net credit. This spread profits if the underlying stays below your short call strike at expiry. The same profit/loss structure applies.

How the payoff works

Three outcomes are possible at expiry for a bull put spread:

• Underlying stays above both strikes. Both puts expire worthless. You keep the entire net premium received. Maximum profit.
• Underlying closes between the two strikes. The short put is in the money, the long put is worthless. You face partial loss — the in-the-money amount minus the premium collected.
• Underlying falls below both strikes. Both puts are in the money and exercise against each other. Maximum loss = spread width − net credit received.

Worked NIFTY example: bull put spread

Suppose NIFTY is at 22,800 (hypothetical, illustrative). You expect it to stay above 22,500 through the weekly expiry. You construct a bull put spread:

• Sell 22,500 put at ₹55
• Buy 22,300 put at ₹22
• Net credit = ₹55 − ₹22 = ₹33 per unit
• Spread width = 22,500 − 22,300 = 200 points
• Maximum loss = (200 − 33) × 75 = ₹167 × 75 = ₹12,525 per lot
• Maximum profit = ₹33 × 75 = ₹2,475 per lot
• Breakeven at expiry = 22,500 − 33 = 22,467

NIFTY needs to fall 333 points from 22,800 — nearly 1.5% — before you hit breakeven. If NIFTY simply stays flat or rises, you keep the full ₹2,475 in roughly 7 days. The reward-to-risk ratio is approximately 1:5, which reflects the high probability nature of this trade (the short strike is well out of the money).

Strike selection: distance, delta, and probability

Choosing where to place your short strike involves a trade-off between premium collected and probability of profit. A short strike with a delta of 0.15–0.25 (15–25% probability of expiring in the money per the Black-Scholes model) gives a high chance of full profit but a smaller credit. Moving the short strike closer to the money (delta 0.35–0.40) collects more premium but narrows your safety buffer.

Most traders benchmark the short put strike against support levels visible on the option chain — strikes with high open interest often act as market floors. Combining technical support with a 0.20–0.25 delta strike gives a reasonable starting framework.

Spread width: wider vs narrower

Wider spreads (e.g., 300 points on NIFTY) collect more absolute premium but require proportionally more margin. Narrower spreads (100 points) use less margin but the long leg costs more relative to the credit received, leaving a thinner net premium. For NIFTY weekly options, 100–200 point spreads are common; for monthly options, 200–300 point widths are typical.

Managing a credit spread through expiry

Credit spreads benefit from theta — time decay erodes the value of both legs, but since the short leg decays faster, the spread value narrows over time in your favour. Common management rules:

• Take profit at 50%. When the spread has decayed to half the original credit, close the position. Releasing capital and margin earlier lets you redeploy into the next opportunity.
• Exit at 2x loss. If the spread widens to twice the original credit received (i.e., the short strike is being tested), close rather than ride to maximum loss.
• Avoid holding through expiry when the short strike is at risk. Assignment risk and pin risk near the short strike in the final hours can create unpredictable outcomes.

Common mistakes

• Placing the short strike too close to the money just to collect a larger credit — without accounting for the higher probability of loss.
• Treating the net credit as "profit already earned" and not monitoring the position. Credit spreads can move against you quickly if the market gaps.
• Ignoring implied volatility at entry. Selling credit spreads when IV is very low means thin premiums and less cushion — high IV environments are generally better for credit spread sellers.
• Not using the matching long leg, thereby converting a spread into a naked short — which dramatically increases both margin requirements and maximum loss.
• Selecting expiries with very little time remaining (1–2 days) without understanding that gamma risk spikes near expiry, making short strikes much more sensitive to spot movement.

Frequently asked questions

What is the maximum profit on a credit spread?

The maximum profit is the net premium received at entry. It is realised when both legs expire worthless — meaning the underlying stays on the favourable side of the short strike through expiry.

How is margin calculated for a credit spread on NSE?

NSE margin for a credit spread equals the spread width minus the net premium received, multiplied by lot size. A 200-point wide bull put spread with ₹33 net credit requires maximum margin of (200 − 33) × 75 = ₹12,525 per lot — far less than a naked short put.

When should I close a credit spread early?

A common rule is to close at 50% of maximum profit. On the loss side, exit when the spread has widened to 2x the original credit to avoid riding into maximum loss near expiry.

What is the difference between a credit spread and a debit spread?

A credit spread collects premium at entry and profits from time decay or a move in your favour. A debit spread requires a premium payment and profits from a directional move. Credit spreads have higher probability of profit but lower reward-to-risk; debit spreads are the opposite.

Keep learning

• Debit spreads explained
• Iron condor guide for NSE
• Option Greeks explained
• What is implied volatility?