Sometimes the goal isn't to bet big on a stock shooting up — it's to collect some income while the stock does roughly what you expect: not much. A bull put spread lets you do exactly that. You generate a credit upfront, and as long as the stock stays flat or drifts higher, you keep it.
Here's how it works.
The basics
A bull put spread is an options strategy that generates income when a stock stays flat or rises, by selling a put and buying a lower-strike put for protection. Also called a credit put spread, it involves two moves at once:
Sell a put option at a higher strike price
Buy a put option at a lower strike price
Both options are on the same stock and expire on the same date.
Selling the put brings in premium — that's your income. Buying the lower-strike put costs some of that back, but it also puts a floor on your losses if the stock drops hard. The result: you know your max gain and your max loss before you place the trade.
Legs of the trade: 2 (long put, short put) Sentiment: Bullish
A real example (with fake numbers)
Let's say Jill has been watching PEAR stock. She thinks the price will stay flat or edge higher — nothing dramatic, just steady. A bull put spread fits: it generates income from that thesis, with built-in protection if she's wrong.
Here's what she does:
Sells 1 PEAR 100 put at $3.20
Buys 1 PEAR 95 put for $1.30
Her net credit (what she collects upfront) is $1.90 per share. With a contract multiplier of 100, that's $190 in her pocket to start.
The upside: maximum profit
If PEAR stays at or above $100 at expiration, both puts expire worthless and Jill keeps the full $1.90 she collected. That's her maximum gain — and it's already sitting in her account.
Question: PEAR is at $101 when Jill sets up her spread for a net credit of $1.90. At expiration, PEAR is trading at $102. What's her profit (before fees and commissions)?
Answer: $190
Both options expire worthless. Jill keeps all the premium she collected.
$1.90 × 1 × 100 = $190
Want to break it down by leg?
Short put (100 strike): Worth $0 at expiration. Jill collected $3.20, so she has a profit of $3.20.
Long put (95 strike): Worth $0 at expiration. Jill paid $1.30, so she has a loss of $1.30.
($3.20) + (–$1.30) = $1.90 × 100 = $190
The downside: maximum loss
PEAR fell hard and Jill's thesis was wrong. The silver lining: she knew exactly how bad it could get when she placed the trade. The long put cushioned the blow, capping her loss at the spread's maximum value.
Quiz: Same setup — PEAR at $101, net credit of $1.90. At expiration, PEAR closes at $93. What's Jill's profit or loss?
Answer: –$310
When PEAR finishes below the lower strike, the spread hits its maximum value — the difference between the strikes ($100 – $95 = $5). Jill sold the spread for $1.90, so:
Premium collected – put spread value at expiration ($1.90) – ($5) = –$3.10 × 100 = –$310
By each leg:
Short put (100 strike): Worth $7 at expiration. Jill collected $3.20, so she has a loss of $3.80.
Long put (95 strike): Worth $2 at expiration. Jill paid $1.30, so she has a profit of $0.70.
(–$3.80) + ($0.70) = –$3.10 × 100 = –$310
The break-even
Question: What's Jill's break-even price per share?
Answer: $98.10
PEAR moved the right direction, just not quite enough. Jill needs the stock to stay above her short put strike, minus the premium she collected. Below that she loses more than she took in; above it, she's in the green.
$100 – $1.90 = $98.10
What Jill is actually hoping for
She wants PEAR to finish at or just above $100 at expiration. If it does, neither put has any value, and she keeps the full credit. The higher PEAR trades, the more comfortable she feels, but the payout stays the same — a quiet, uneventful expiration is exactly what she's rooting for.
How time and volatility move the trade
Two forces work in the background of every bull put spread: the passage of time and changes in implied volatility (IV).
Time decay works in your favour. Because you collected a net credit, each day that passes chips away at the value of the options you're short — nudging the spread toward its maximum profit as long as the stock holds above the higher strike.
Falling volatility helps, rising volatility hurts. When IV drops, option premiums shrink and the spread you sold gets cheaper to close — good for you. A spike in IV does the opposite, inflating the value of the puts and widening a potential loss.
Put simply: a quiet, sideways-to-higher market is the friendliest backdrop for this trade.
A risk to keep on your radar: early assignment
Because Jill sold a put as part of this spread, she carries early assignment risk. The buyer of the put she sold can exercise it early — any business day before expiration — and Jill has no control over the timing.
Here's what matters:
Her long put (lower strike) has no early assignment risk. She decides if and when to exercise it.
Her short put (higher strike) does carry early assignment risk.
The most common reason someone exercises a put early is to get the strike-price cash sooner — selling the shares at the strike now lets them earn interest on that money. This mainly happens when the put is deep in-the-money and has little time value left, so exercising gives up almost nothing. When the interest to be earned outweighs the option’s remaining time value, it can make sense to exercise early.
If Jill thinks early assignment is likely, she has two options:
Close the entire spread — buy back the short put, sell the long put
Buy back just the short put and leave the long put open
If she gets assigned on the short put, she's on the hook to buy PEAR shares at $100. If she planned to exercise her long put to exit that stock position, she needs to know the sale date will land one day after the purchase date — which means extra fees and potential interest charges. Assignment can also trigger a margin call if there isn't enough equity in the account to support the resulting stock position.
One thing worth noting: the higher-strike put can be in the money without the lower-strike put being there too. So if Jill gets assigned on the short put, she could end up holding long stock with a long put that's still out of the money — a position she wasn't planning for. Know your plan before expiration, not after.
Also: options are exercised at expiration if they're at least $0.01 in the money — unless you tell your broker not to (the OCC calls this “exercise by exception”). As expiration gets close:
If PEAR is near $100, assignment on the short put is uncertain
If PEAR is near $95, assignment on the short put is almost certain — and whether the long put gets exercised is the question
If Jill wants to avoid ending up with stock after expiration, she should close the spread before it expires.
Putting it all together
A bull put spread is a way to generate income from a stock you think will hold steady or move higher — without needing to own the shares. Your upside is the premium you collect, and your downside is capped. And you know both numbers going in.
Next up: explore how other income-generating strategies like iron condors and covered calls can complement this approach.