Rights versus obligations

Every option contract has two sides, and the two sides are not symmetrical. One side pays money up front and gets a choice. The other side collects that money and takes on a duty. Almost everything confusing about options gets simpler once you keep that asymmetry in view.

The four positions

A call is the right to buy a stock at a fixed price (the strike) on or before a fixed date (expiration). A put is the right to sell at the strike on or before expiration. For each, someone is the buyer and someone is the seller (also called the writer), which gives four basic positions:

The buyer's downside is capped at what they paid. The seller's downside is whatever it costs to fulfil the obligation, which for a short call on a stock is theoretically unlimited and for a short put is the full strike price times 100.

A worked example

Stock XYZ trades at $50. A one-month call with a $52 strike is offered at $1.50. You buy one.

• You pay $1.50 × 100 = $150. That is the most you can lose.
• If XYZ is at $56 at expiration, your right to buy at $52 is worth $4 per share, or $400. Profit is $400 − $150 = $250.
• If XYZ is at $52 or below at expiration, the right to buy at $52 is worth nothing. You lose the $150.
• Your breakeven at expiration is $52 + $1.50 = $53.50.

Now look at the other side. The seller collected $150. If XYZ finishes at $56 they must deliver 100 shares at $52 while the market says $56, a $400 obligation against $150 received, net loss $250. If XYZ finishes at $60, the loss is $800 − $150 = $650. There is no ceiling.

Payoff at expiration

Long $52 call, paid $1.50
                                    /
  P&L                              /
  +250 |                          /
     0 |------------------------X---------  X = breakeven $53.50
  -150 |________________________/
       +----+----+----+----+----+----+---
       48   50   52   54   56   58   60   stock at expiry

The flat line is the premium lost. The kink at $52 is where the option starts to have value. The seller's picture is the mirror image: flat profit of $150 to the left, unlimited loss sloping down to the right.

Key idea: Buying an option buys a choice; selling an option sells a promise. The buyer knows the maximum loss the moment the trade fills. The seller does not.

"Limited risk" is not the same as "low risk"

Beginners hear "you can only lose the premium" and read it as "safe". The premium is 100% of the money in the trade. Long options lose their entire value routinely, not occasionally. Limited risk means you know the worst case in advance, which is valuable. It does not mean the worst case is unlikely.

Sellers have the opposite trap. Collecting premium feels like being paid, and most of the time the option expires worthless and the seller keeps it. The occasional loss can be a multiple of every premium collected that year. Module 7 goes into why "income" is never free.

Exercise, assignment and the clearing house

When a buyer uses their right, that is exercise. When a seller is chosen to fulfil it, that is assignment. You are not matched against the specific person who took the other side of your trade; a clearing house (in the US, the OCC) stands in the middle, guarantees both sides, and randomly assigns exercises to short holders. That is why counterparty risk on listed options is not something you need to think about, and also why assignment can arrive on any short option that is in the money, at any time, without warning.

Most options are never exercised. They are either closed before expiration by an offsetting trade (sell what you bought, or buy back what you sold) or they expire worthless. Closing a position is the normal way out.

Try it: Pick any liquid stock and look at the option chain. Find a call one strike above the current price and a put one strike below. For each, write down the maximum loss for the buyer, the maximum loss for the seller, and the breakeven at expiration. Do this with real prices; the numbers will make the asymmetry obvious.

Recap

• A call is the right to buy at the strike; a put is the right to sell at the strike; both have a buyer with a right and a seller with an obligation.
• The buyer's maximum loss is the premium paid; the seller's maximum loss is the cost of fulfilling the promise, which can dwarf the premium.
• Breakeven for a long call is strike plus premium; for a long put, strike minus premium.
• Limited risk means the worst case is known, not that it is rare. Long options expire worthless often.
• Exercise is the buyer's action, assignment is the seller's fate, and a clearing house guarantees both sides.