Home › Comparisons

Exercise vs assignment: the buyer acts, the seller lives with it

Exercise and assignment are two sides of one event. The option buyer exercises, which means they use their right. The option seller is assigned, which means they must keep their promise.

Comparison · 5-minute read · Updated 2026-10-26

The short answer

Exercise is something the option buyer does. They use their right to buy shares at the strike (a Call option) or sell shares at the strike (a Put option).

Assignment is what happens to the option seller. When a buyer exercises, a seller somewhere is picked to fill the order. That seller must sell or buy the shares at the strike. See Assignment.

The buyer has a choice. The seller has an obligation. As a wheel seller, you live on the assignment side.

Side by side

How a buyer's exercise finds you

You never know who bought your option. The trade goes through a clearing house, the Options Clearing Corporation (OCC), which stands between buyers and sellers.

When a holder exercises:

1. The holder's broker sends an Exercise notice to the OCC.
2. The OCC assigns it to a broker that has customers short that same option. This is done at random.
3. That broker picks one of its short customers, by a method it discloses, such as random or first-in-first-out.

So you can be assigned even if "your" buyer never exercised. Any holder of that option can trigger it, and the notice can land on any seller.

What happens at expiry

At expiry, you don't need anyone to choose. The OCC exercises options that end in the money by a small amount unless the holder tells their broker not to. This is called Automatic exercise.

That's why a short option that closes even a few cents in the money is very likely to be assigned. And why one that closes right at the strike is a coin toss. See Pin risk.

A worked example (an illustration, not a trade idea)

You sell a $45 put on a made-up stock, XYZ, for $1.00. You collect $100. Somewhere, a buyer pays that $100 for the right to sell you 100 shares at $45.

At expiry, here's what each side sees:

In every row, you keep the $100 premium. Assignment doesn't take it back. What changes is the value of the shares you had to buy.

The buyer, in the $30 row, gained most of what you lost. Options are a transfer between the two sides.

Can you exercise as a seller?

No. You don't have a right to use. You sold it. The only way out of your obligation before assignment is to buy to close: buy the same option back, so you're no longer short. See buy to close vs letting it expire.

If you're short an option and you'd rather not be assigned, close or roll it before the holder has a reason to exercise. Once the notice arrives, it's done.

Why this matters for the wheel

In the wheel strategy, assignment is part of the plan. A put assignment gives you shares. A call assignment sells them. The cycle depends on it.

That only works if you treat every short option as a promise you'd be fine keeping. Ask before you sell: "If the holder exercises tomorrow, am I okay?" If not, the trade is too big, or the strike is wrong.

In Canada, the same rules apply to US-listed options in a TFSA or RRSP, as long as your broker allows the strategy in that account.

Questions