Bull Put Spread

Quick answer: A Bull Put Spread sells a higher-strike put and buys a lower-strike put of the same expiry for a net credit, a moderately bullish position that keeps the credit if the underlying holds above the short strike.

In simple words

You sell a put to collect premium, betting the market stays up, then buy a lower put as insurance so a fall cannot hurt you without limit. You keep the money you collected if the market holds above the strike you sold. If it falls through, the put you bought caps the damage. Unlike buying a spread, here you are paid up front and you win simply by the market not dropping — but the amount you can lose is larger than the amount you can keep, so it needs to be right more often than wrong to come out ahead.

Payoff diagram

Professional explanation

The same shape as a bull call spread

A bull put spread and a bull call spread draw the identical payoff diagram: bullish, defined risk, capped profit, capped loss. What differs is the cash flow and the internals. The put version is opened for a credit and is net-short vega and net-long theta, so it gains from the underlying holding still and from volatility falling. The call version is a debit, net-long vega and short theta, and needs the market to actually rise. They use different strikes to sit in the same place. Neither is superior; the choice turns on volatility view, cash flow and, on stock options, which leg carries assignment risk. The comparison lives at /compare/bull-call-vs-bull-put.

Why the loss is larger than the profit

The most you can make is the net credit; the most you can lose is the strike width minus that credit. Since the credit is usually the smaller number, the risk exceeds the reward — often by two or three to one. That is not a flaw to be fixed but the price of a position that profits from the underlying merely not falling. It means the trade has to win more often than it loses simply to break even, and a single move through the short strike can give back several winning trades' worth of credit.

Where the cap comes from

The long lower-strike put is what makes this defined-risk. Without it, selling the higher put would be a naked put whose loss runs all the way down toward the underlying reaching zero. The long put stops the bleed: below its strike, further falls in the underlying are matched rupee-for-rupee, so the payoff stops declining. The distance between the strikes therefore sets the maximum loss, and buying the long put closer to the short one narrows both the risk and the credit received. This is the single structural difference between a bull put spread and a naked or cash-secured put — the same short put, but with a defined floor bought beneath it — and it is why the two attract very different margin and carry very different tail risk despite sharing a leg.

Assignment is a live risk here

The short leg is a short put, and on American, physically settled stock options it can be assigned early if it goes in the money — handing the trader stock and cash outflow before expiry, with the long put as only partial cover. On European, cash-settled index options like NIFTY there is no early assignment and settlement is in cash. Even so, letting an in-the-money short put settle rather than closing it can trigger STT on the settled leg, and pin risk applies if the underlying finishes exactly at the short strike.

Construction

1. Sell one out-of-the-money or at-the-money put of the chosen expiry to collect premium.
2. Buy one lower-strike put of the same expiry and quantity as protection.
3. The net credit is the maximum profit; the strike width minus the credit is the maximum loss.

Market outlook

A trader may study a bull put spread when the view is that the underlying holds above a level over the next few weeks — flat-to-rising is enough, since the credit is kept as long as it does not fall through the short strike. Because it collects premium, it sits more comfortably when implied volatility is high and puts are richly priced, so the credit is fuller and time decay works for the position. The view is invalidated by a decline through the short strike, where losses mount toward the capped maximum. It is the wrong shape when a sharp fall is feared, since the reward is small relative to the defined but larger loss.

Risk profile

This is a defined-risk position. The maximum loss is the strike width minus the net credit, capped by the long lower-strike put: below that strike the payoff stops falling because further declines are matched by the long put. Without the long put the short put would be undefined-risk, losing all the way toward zero. The cap is structural, not a stop order. On index options it holds cleanly; on stock options the short put's early-assignment risk can hand the trader shares and disturb the defined-risk profile until the position is closed. The loss is larger than the credit, so risk sizing matters.

Reward profile

The maximum profit is the net credit received, kept in full if the underlying settles at or above the short put strike at expiry. There is no gain beyond the credit no matter how far the underlying rises, so the reward is fixed and modest. Between the strikes the profit shrinks from the full credit toward the maximum loss. The appeal is that the position can profit from the underlying simply holding still or drifting up, aided by time decay, rather than requiring a directional move.

Margin requirement

As a defined-risk spread the long put caps the short put, so margin is charged on the spread — broadly the maximum loss (width minus credit) — rather than full naked-put margin, which would be far larger. SPAN plus exposure applies and is reduced by the hedge. NSE and brokers revise margin and hedge benefits periodically, so confirm the current requirement; a naked short put in the same underlying would demand substantially more.

Greeks exposure

The sign on each Greek above is computed, not asserted: it is the net exposure of the illustrative legs at spot 24,000 with 30 days to expiry, priced with Black–Scholes using each leg's implied volatility calibrated from its own quoted premium. A sign can flip as the underlying moves — the panels below show where. See Methodology.

Volatility impact

Rising implied volatility inflates the nearer-the-money short put more than the long put, so the spread is net-short vega and loses ground when volatility climbs — the mark-to-market can worsen even before price moves. Falling volatility helps, which is why the position is more comfortable to open when implied volatility is elevated and expected to ease, for example after a feared event passes. A volatility spike accompanying a fall through the short strike is a double blow: direction and vega both turn against the trade at once, pushing it toward its capped maximum loss faster than price alone would suggest.

Time decay

Time decay works for the position while the underlying stays above the short strike, because it is a net credit and theta is positive. Each day that passes with the underlying holding up erodes the short put in the trader's favour faster than it erodes the long put. The benefit is strongest as expiry nears and the short put is out of the money. If the underlying is below the short strike near expiry, decay stops helping and gamma dominates, so small moves swing the profit and loss sharply.

Practical examples

Lot sizes used above (NIFTY 75, BANKNIFTY 30) are those in force at the time of writing; NSE revises them periodically. Figures exclude brokerage, STT, exchange charges, stamp duty and GST, all of which materially affect small spreads.

Common mistakes

• Treating the credit as the risk: the amount that can be lost is the width minus the credit, often two to three times the premium collected, so a single bad trade can erase several good ones.
• Selling the short strike too close to the money for a fatter credit, which raises the chance of the underlying falling through it and realising the capped loss.
• Assuming the position is safe because it is defined-risk, when in fact a fall through the short strike moves quickly toward the larger maximum loss, worsened by any volatility spike.
• On stock options, ignoring that the short put can be assigned early and deliver stock plus a cash outflow before expiry, breaking the tidy spread.
• Letting an in-the-money short put run to settlement to save a commission, incurring STT on the settled leg that can exceed the cost of closing it.
• Opening it in low implied volatility, where the credit is thin relative to the width and the reward barely compensates for the defined but larger risk.

Advantages & disadvantages

Adjustments & exits

• Rolling the spread down and out to a later expiry after the underlying weakens can defer the loss and collect more credit, but extends risk and is not a certain recovery.
• Buying back the short put and holding the long put after a sharp fall converts the position to a long put, trading the collected credit for downside participation.
• Rolling the long put up closer to the short strike narrows the width and reduces both the risk and the margin, at the cost of a smaller net credit.
• Closing the spread once most of the credit has decayed away locks the gain and avoids expiry-week gamma and settlement costs.

Adjustment is a decision about risk, not a way to rescue a losing view. See Adjustments and Exit Planning.

Professional usage

Desks and funds sell put spreads to harvest premium and time decay while capping the tail that a naked put leaves open, using the defined width to size risk across a book. The structure is a common way to be paid for the view that an index or name holds a level, with the long leg turning an open-ended short into a bounded one that margin systems treat kindly. Institutions can manage the short leg's assignment and settlement mechanics on single stocks that retail cannot easily handle. The concept — collect a credit, cap the downside, profit from time — scales from one lot to a large overlay.

Frequently asked questions

Voice search & related questions

Natural-language questions people ask about the Bull Put Spread.

Sources & references

• NSE — Options basics
• SEBI — Investor education
• L. McMillan, Options as a Strategic Investment

Last reviewed 9 July 2026. Educational content only — not investment advice.