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What is assignment in options, in plain words?

An option assignment is the seller's obligation to fulfil the terms of the contract when a buyer exercises 1. The seller of a put must buy the stock at the strike; the seller of a call must deliver stock at the strike 1. For American-style options it can happen on any day the short position is open, though most exercises and assignments come on or near expiry 1. European-style options, such as most index options, can be exercised only in a set period just before expiry, so assignment comes only then 1.

A $48 put sold for its model price, or a $52 call sold against 100 shares bought at $50, each with 30 days left at 30% implied volatility (made-up numbers). Choose one and move the stock on the day you are assigned.

Source: the StrikePath engine, pricing with the Black–Scholes formula 2 at 4.3% interest a year; a simulated example, not market prices. For learning; not advice.

In numbers

By the formula the $48 put sells for $0.81 a share, $81 a contract 2. Assigned with the stock at $45, you pay $4,800 for 100 shares worth $4,500 1: with the $81 kept, a loss of $219 before fees. The $52 call sells for $0.99 2; assigned, you deliver the 100 shares and receive $5,200: with the premium, a gain of $299 a contract whatever the stock did above $52, and the rest of the rise is gone 3.

How it reaches you

The clearing house (OCC) assigns exercise notices at random to firms with a short position, and the firm assigns the notice to one of its customers with that contract 1. At expiry, an option a cent or more in the money is normally exercised automatically unless instructed otherwise 4, so a sold option in the money at the close is very likely to be assigned, though its holder can instruct otherwise. The day before a stock goes ex-dividend is the usual time for early assignment of a call 3.

What this shows, and what it doesn't

The arithmetic of one assignment, before fees. A cash-secured put sets aside the cash to buy the shares 5; a call sold without the shares behind it must buy them at the market to deliver, and its loss can have no limit 6.

Go further

What is a cash-secured put? →The sold put, with the cash set aside.American and European options →When assignment can come.
Sources (6), checked 20 October 2026 and 27 October 2026
  1. FINRA, “Trading Options: Understanding Assignment” (14 December 2020). Read it (read 27 October 2026)
  2. Fischer Black and Myron Scholes, “The Pricing of Options and Corporate Liabilities”, Journal of Political Economy 81(3), 637–654, 1973. Read it (read 20 October 2026)
  3. The Options Industry Council, “Covered Call (Buy/Write)”. Read it (read 27 October 2026)
  4. US Securities and Exchange Commission, Release No. 34-57163 (16 January 2008), approving OCC's change to exercise by exception, 73 FR 4298. Read it (read 20 October 2026)
  5. Montréal Exchange, “Cash-Secured Put” (equity options strategy sheet). Read it (read 27 October 2026)
  6. CME Group, “Covered Calls” (Option Strategies course). Read it (read 27 October 2026)

Now try it on a scenario of your own

Pick where a simulated stock might be, and by when: drag one dot and see, side by side, what buying shares, one option, or a pair of options (a call or put spread) would each do. Free, no sign-up.

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