What selling premium is
Every option has two sides. The buyer pays the premium and receives a right; the seller (or writer) collects that premium and takes on the matching obligation. "Selling premium" names any structure built from the seller's side.
Two mechanics follow directly. First, the payoff is inverted: a buyer has bounded cost and open-ended upside, so the seller has bounded gain — the premium collected — and a much larger obligation on the other side. Second, theta runs in the seller's favour: the extrinsic value that decays away is value the buyer loses and the seller, having already collected it, keeps as the option approaches expiry worthless. A sharp move against the position is the exposure that pays for that tailwind.
This is a risk shape, not a recommendation. What follows describes what each structure obligates the seller to — nothing here says the trade is a good one.
The three common structures
- Covered call — sell a call against stock you already own. If price rises through the strike, your shares are called away at that strike: your upside is capped there, and you keep the premium. The obligation is covered by the shares, so the risk is the ordinary risk of owning the stock, minus the premium collected, with the upside capped.
- Cash-secured put — sell a put with cash set aside to buy the stock at the strike if assigned. If price falls through the strike, you are assigned and buy the shares at that strike (effectively at strike minus the premium). If it does not, you keep the premium. The obligation is secured by the reserved cash.
- The wheel — not a new instrument, just the two above in sequence: sell cash-secured puts until assigned, then sell covered calls on the assigned shares until they are called away, and repeat.
A worked example
Take a generic instrument — call it GENCO — trading at 100.
Covered call: you own 100 shares and sell the 105 call for a 2.00 premium. Two branches: if GENCO finishes above 105, the shares are called away at 105 — your gain is the 5 points to the strike plus the 2.00 premium, and no more, however high it went. If it finishes below 105, you keep the shares and the 2.00; the shares themselves can still fall, and the premium offsets only the first 2 points of that decline.
Cash-secured put: you set aside 9,500 and sell the 95 put for 2.00. If GENCO finishes below 95, you are assigned and buy at 95 (a 93.00 effective cost after the premium), and you carry the stock down from there. If it finishes above 95, the put expires and you keep the 2.00.
The wheel chains these: puts until assigned, calls until called away. In each leg the gain is bounded by the premium and any capped stock move, and the larger exposure is a move against the position. That asymmetry is the structure — read it as the shape of the obligation, not as a case for taking it.
See it in kestrel
Read how a written option behaves across a real, recorded session instead of a single payoff line:
npx kestrel.markets sim mean-reversion-range-fadeThat runs a deterministic simulation over a generic range-bound session — managed licensed data, no wall time, no signup, no card — and prints a certified proof URL. Recompute the whole record on your own machine, byte for byte:
npx kestrel.markets certify https://kestrel.markets/proof/art_f576347572a410a52647cf90Keep the tool one command away: drop the kestrel.markets MCP server into your client and the next session you want to read is already wired up — no account in between.