Execution
Execution is the moment an order is actually filled — when a matching buyer or seller is found and the trade takes place at a specific price.
Execution is the moment your order actually trades. Until then it is only an instruction. The price you get, how fast it happens and whether the whole order fills all depend on where the broker sends it and what is in the market at that moment. Rules on how brokers must handle orders differ by country.
- Category
- Order Types
- Reading time
- 3 min
- Also called
- Order execution, Trade execution, Fill
- Updated
Execution in plain words
When you press “buy” or “sell”, the order goes to your broker over the internet, and the broker chooses the market where it will be filled.1
Prices can change in transit, so by the time the order arrives the price may be a little — or a lot — different.1
In the US, FINRA Rule 5310 requires brokers to make a real effort to find the best market for each order.2
How an order gets executed
You send the order
Choose the instrument, side, size and order type.
Broker routes it
The broker routes the order to the venue it chooses.1
Best execution duty
The broker must aim for the best execution reasonably available.1
Matching
The venue matches your order against an opposite order.
Fill or part fill
If not enough shares are available, you may get only part of the order filled — a partial fill.3
Confirmation
You receive the execution price, size and time; check it against your order.
Worked examples
Example 1 — Market order
−3.00A hypothetical trader buys 100 shares with a market order while the quote shows 20.00.
| Quoted | 20.00 |
| Executed | 20.03 |
| Extra cost | 0.03 × 100 = 3.00 |
A market order normally fills right away, though not always at the price you saw.4
Example 2 — Fast market
Price movedA hypothetical stock moves 1% in the second it takes the order to arrive.
| Move | 1% |
The price moved while the order was on its way, so the fill was different from the quote.1
Example 3 — Limit order
PartialA hypothetical buy limit at 15.00 for 300 shares; only 120 are offered at that price.
| Filled | 120 |
| Open | 180 |
Only some of the shares were available, so the order was partly filled.3
Market vs limit execution
| Aspect | Market order | Limit order |
|---|---|---|
| Speed | Usually immediate | Only at limit or better |
| Price | Not guaranteed | Capped |
| Fill risk | Low | May not fill |
| Best for | Liquid markets | Thin markets |
Where execution matters
Costs
Execution quality drives Slippage.
Order choice
Choosing a Market Order or Limit Order.
Spreads
Crossing the Bid-Ask Spread.
Fees
Execution adds Trading Fees and Commissions.
Advantages and disadvantages
Advantages
- Turns a plan into a real position.
- Brokers must seek good terms for clients.
- Order types let you control price or speed.
Disadvantages
- The fill price can differ from the quote.
- Fast markets cause slippage.
- Large orders may fill only in part.
- Routing is not visible to most clients.
Going deeper
Read as far as you need. Each level builds on the one before it.
Routing
Beginner
Clicking the button only sends the order to your broker; the broker decides where it is executed.1
Timing
Intermediate
US rules set no fixed time limit within which a trade must be executed.1
Best execution
Advanced
US brokers must make a real effort to find the best market and to get the best execution reasonably available.1 Rules differ by country.
Common mistakes
Assuming the quote is the fill
Check the execution report.
Market orders in thin markets
Use limits.
Ignoring partial fills
Check the remaining size.
Not reviewing costs
Compare fills over time.
Check your understanding
Test yourself before moving on. Each answer comes with an explanation.
Key points to remember
- Execution is when the order actually trades.
- The broker routes the order.
- Fill price can differ from the quote.
- Orders can fill in part.
- Best-execution rules differ by country.
Frequently asked questions
Is execution instant?
What is a fill?
Can I choose the venue?
Further learning
- Order
Order basics.
- Slippage
Fill vs quote.
- Limit Order
Price control.
- Order Book
Where orders meet.
Sources
This article is written in our own words. The sources below support the specific facts, rules and figures marked with a number in the text. Links open the original publisher’s page.
- U.S. SEC. Trade Execution: What Every Investor Should Know (opens in a new tab) Checked .
- FINRA. Rule 5310. Best Execution and Interpositioning (opens in a new tab) Checked .
- FINRA. Trading Terms: Time Parameters and Qualifiers on Stock Orders (opens in a new tab) Checked .
- Investor.gov (SEC). Understanding Order Types – Investor Bulletin (opens in a new tab) Checked .
Educational content, not financial advice. Examples use hypothetical prices and simplified costs; actual fees, margin rules and regulations vary by broker, market and country. We are not affiliated with any publisher linked above. Last reviewed . Report an error or request a source credit.