A fill is the execution of an order, the moment it is matched against another trader and the trade actually happens, turning an instruction into a position.
Last reviewed 7 October 2025 · Educational, not advice
When you place an order you are sending an instruction to buy or sell. Nothing has traded yet. A fill is the moment that instruction is matched against another participant willing to take the other side, so an actual trade occurs and you receive the contracts you wanted, or sell the ones you held. If your whole order trades, you are fully filled. Until then the order is only a request, not a position.
Orders do not always fill in one piece. A partial fill happens when only some of your order executes because there was not enough size available at your price. You end up holding a smaller position than you asked for. With a limit order the remainder usually rests in the book and waits for someone to meet it. With other order types the unfilled part may be cancelled. Knowing which behaviour applies on your platform matters, because a partial fill can leave you with a different position than you intended.
The price at which you fill can differ from the price you saw on screen. A market order asks to trade now against whatever the book offers, so in a thin market it can trade through several price levels and leave you with an average fill worse than the first quote. That gap between the expected and the actual price is called slippage. A limit order avoids it by refusing to fill beyond the price you set, but it accepts the risk of not filling at all if no one meets your price.
A fill is an execution, not a result. Being filled simply means your trade went through and you now hold a position. It says nothing about whether that position will make or lose money, which depends on how the price moves and how the contract resolves. From the moment you are filled, the money you have committed is genuinely at risk, so it is worth checking your fills carefully and understanding the order types your platform offers before you trade.
You place a market order to buy one hundred yes contracts. The book shows forty available at forty cents and the rest only at forty two cents. You are filled on forty contracts at forty cents and sixty at forty two, an average of about forty one cents rather than the forty you first saw. That difference is slippage. Had you placed a limit order at forty cents instead, you would have been filled on forty contracts and the remaining sixty would rest in the book, a partial fill, until a seller met your price or you cancelled.
Illustrative only. Numbers are examples, not a quote or a prediction, and exclude fees.
A fill means your trade executed, not that it will profit. From that moment the money is at risk and any position can lose. Stake only what you can afford to lose, never to chase a loss, and never on borrowed money. If it stops feeling like a free choice, step back. In the United States you can call or text the helpline on 1-800-GAMBLER or visit ncpgambling.org.
A fill is the execution of an order, the moment it is matched against another trader and a trade actually happens. When all of your order trades you are fully filled. Until that happens, an order is just an instruction sitting in the book.
A partial fill is when only some of your order executes because there was not enough size available at your price. You end up holding a smaller position than you asked for, and the rest either rests in the book waiting or is cancelled, depending on the order type.
On a market order in a thin book, your order can trade through several price levels, so the average fill price is worse than the first quote you saw. That gap is called slippage. A limit order avoids it by refusing to fill beyond your set price, at the risk of not filling at all.
No. A fill only means your trade executed and you now hold a position. Whether it gains or loses depends on how the price moves and how the contract resolves. The money at stake is genuinely at risk from the moment you are filled.
The rules change fast. Get the changes that affect you, plain and current, not tips.
Independent. Every claim dated and sourced. No platform pays for its place.