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The YES/NO model

Every market on Polymarket US has two sides: YES and NO. They always add up to $1.00. If YES is priced at $0.60, NO is priced at $0.40. You don’t trade YES and NO as separate things. There’s only one instrument per market — the YES side. To trade against an outcome, you sell YES (which is the same as buying NO).
What you want to doHow you do it
Trade on the outcome happeningBuy YES
Trade on the outcome not happeningSell YES (equivalent to buying NO)
Close a winning YES positionSell YES
Close a losing NO positionBuy YES back
This matters because when you place an order, the price always refers to the YES side. If you want to buy NO at $0.40, you’re really selling YES at $0.60 — the system handles this, but you need to understand it to set the right price.

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Order types

TypeHow it works
Limit orderYou set a price. The order sits on the book until someone trades against it, or you cancel it.
Market orderFills immediately at the best available price. You get instant execution but pay the spread.
Most traders use limit orders. Market orders are useful when you need to get in or out quickly and don’t mind paying a slightly worse price.

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Time in force

When you place a limit order, you choose how long it stays active:
OptionWhat it means
Good till cancel (GTC)Stays open until it fills or you cancel it
Good till date (GTD)Stays open until a specific time, then cancels automatically
Immediate or cancel (IOC)Fills whatever is available right now, cancels the rest
Fill or kill (FOK)Must fill completely or not at all — no partial fills

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What happens after you place an order

Your order goes through a lifecycle:
  1. Pending — the exchange has received your order
  2. Open — it’s resting on the book, waiting for a match
  3. Partially filled — some of your order has matched, the rest is still open
  4. Filled — your entire order has matched
  5. Canceled / Expired / Rejected — the order didn’t fill

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Positions

Once your order fills, you have a position. A position is simply the contracts you hold in a market.
  • A long position means you own YES contracts — you profit if the outcome happens
  • A short position means you’ve sold YES contracts — you profit if the outcome doesn’t happen
Your buying power is the cash you have available to open new positions. When you buy contracts, your buying power decreases. When you sell or a market settles in your favor, it increases.

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Closing a position

You can close a position at any time by taking the opposite action:
  • If you’re long (bought YES), sell YES to close
  • If you’re short (sold YES), buy YES to close
You don’t have to wait for the market to settle. If the price has moved in your favor, you can lock in a profit early.