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Placing a Trade

4 min read

This page covers how to buy and sell an outcome on a market detail page (/market/[slug] or /m/[conditionId]). Every order is placed as a number of shares, and a share pays out $1 if that outcome wins. When buying you can type the size either in Shares or as an Amount in dollars; the panel converts an amount to shares for you.

Note

Orders placed here are real Polymarket orders. Prices update continuously, so the panel lets you choose how much price movement you accept: a Max slippage cap on market orders, or an exact price with a limit order. Nothing here is investment advice.

#Choosing an outcome

Every market has outcome buttons — Yes / No for a binary market, or a set of named buttons for a multi-outcome market (for example team names on a moneyline, or Over / Under on a total). The labels match the raw outcome text shown in the live-trades feed, so the button you click reads the same as the trade it produces.

The price on each button, in the order book, and in the percentage figures is the real last trade price — not a fabricated midpoint. The header price flips depending on the order type: a market order shows the price you would actually touch (a buy crosses to the best ask, a sell to the best bid), while a limit order shows the last trade clamped into the live spread.

#Order types

Type Behavior Fee
Market Crosses the book and fills within seconds at the best available price (fill-or-kill). Pays Polymarket's taker fee plus BOOPOLY's 0.5% platform fee, both auto-applied.
Limit Rests at the price you choose until it fills or you cancel. No fees when it fills as a maker (no platform fee, no Polymarket taker fee); may never fill if the market moves away. A limit price that crosses the book fills at once as a taker and pays the taker fees.
Note

On a wide book, a market order can fill slightly away from the shown price. The panel points this out when the spread is wider than 5¢, and the Max slippage cap rejects any fill worse than your setting instead of executing it. See Fees for how the fees are calculated.

#Setup flow — market buy

  1. Open the market and click the outcome you want (Yes / No or a named button).
  2. Set the order side to Buy and the order type to Market.
  3. Enter the size — switch between Amount (dollars) and Shares under the figure. Use the −/+ buttons, or Max to size to your balance net of fees.
  4. Optionally adjust Max slippage (1% to 5%, scroll for 10% / 20% / 40%; 2% by default). A worse fill is rejected.
  5. Review the order summary — Total cost, and the Fee breakdown behind the ⓘ next to it, where Polymarket's taker fee and the platform fee appear together as one Fees line.
  6. Click Buy. Your USDC balance is auto-wrapped to pUSD collateral and the order fills at the best book price.
Tip

Polymarket's minimum order is 5 shares and $1, so on a cheap outcome the minimum is more than 5 shares; the panel shows the minimum and won't submit a smaller buy. For a market buy close to that minimum (about 6 shares or fewer), BOOPOLY adds a small (~1.5%) buffer to the amount so the fill lands at or above 5 shares and the position stays sellable.

#Setup flow — limit buy

  1. Open the market and click the outcome you want.
  2. Set the order side to Buy and the order type to Limit.
  3. Set your Limit price in cents. Auto follows the best resting price on your side of the book (the best bid for a buy) and keeps following it; type a price, or step it one tick at a time with the − / + chips, to set it yourself.
  4. Enter the size (Amount or Shares).
  5. Optionally set an Order expiry (auto-cancel): Never (GTC), a preset (1, 5, 15 or 30 min, 1 h, 24 h), or Custom. An expiry posts the order as GTD so it cancels itself.
  6. Review the summary and click Buy. The order rests on the book until it fills or you cancel it.
Note

A limit buy is a resting order. It only fills if the market trades at your price, so it may sit unfilled indefinitely. Selling works the same way — switch the side to Sell and enter shares up to what you hold (sells are always entered in shares; quick buttons fill 25%, 50% or Max).

#How collateral and balance are handled

  • Orders carry shares. Buy and sell, market and limit, are placed as a share count — cost is shares × price. An Amount you type is converted to shares (rounded down, so it never costs more than you typed).
  • Auto-wrap. On placing an order, your USDC balance is wrapped 1:1 into pUSD collateral (reversible on withdrawal), so orders don't stall mid-flow to convert funds.
  • Pre-flight collateral check. Before a resting limit buy is placed, BOOPOLY checks that your resting buys plus the new order fit within your available collateral. This keeps your existing resting orders in place (otherwise the exchange could auto-cancel one to fund the new order), and the panel tells you when a buy would exceed your free collateral.
Note

Trading is turned off on a market that is closed or resolved; browsing stays open. Real-money trading is not available in some countries and regions, where browsing and simulated trading remain available. If you see Unavailable in your region, order placement isn't available from your current location; your funds and positions are not affected.