# Best Execution and Execution Quality

> Best execution is a broker's duty to get you the most favourable terms on orders. Learn what it covers, price improvement, routing reports and how to judge fills.

Source: https://learn.tradelabsai.com/orders/best-execution/  
Track: Orders and Execution · Level: Intermediate · Updated: 2026-10-03  
Publisher: TradeLabs AI (https://tradelabsai.com). Education, not financial advice.  
Cite as: TradeLabs Learn, "Best Execution and Execution Quality", https://learn.tradelabsai.com/orders/best-execution/

Best execution is a broker's obligation to seek the most favourable terms reasonably available for a customer's order. It is not just about price. It also covers speed, the likelihood of execution, the size of the order and the total cost. For traders, understanding best execution helps you judge whether "commission free" is really cheap and whether your broker is filling your orders well.

## What best execution covers

Regulators describe several factors a broker must weigh:

| Factor | Question |
|---|---|
| Price | Did the order get the best price available, or better? |
| Speed | Was it executed promptly? |
| Likelihood of execution | Did it actually fill, especially limit orders? |
| Size | Could the full order be filled without moving the price? |
| Costs | Commissions, fees and spreads |
| Market character | Was the stock liquid or thin, calm or volatile? |

In the United States, FINRA Rule 5310 sets out the duty for broker-dealers. In Europe, MiFID II requires firms to take all sufficient steps to obtain the best possible result. Neither rule guarantees a specific price; they require a reasonable process and regular review.

## Price improvement

Price improvement means getting a better price than the displayed best quote.

**Example: Measuring price improvement**
The national best bid and offer is $50.00 by $50.04. You send a market buy for 100 shares and are filled at $50.03. You received 1 cent of price improvement per share, $1 in total. On a sell at $50.01, you would also have received 1 cent of improvement over the $50.00 bid.

Wholesale market makers often provide small price improvement on retail orders. Brokers publish statistics on how often and by how much their customers' orders are improved.

## Routing and conflicts of interest

Brokers may route orders to venues that pay them, through payment for order flow or exchange rebates. That creates potential conflicts with best execution, which is why rules require brokers to disclose routing practices and compare execution quality across venues regularly. In the US, SEC Rule 606 reports show where brokers route orders and what they receive, and amended Rule 605 reports cover execution quality statistics. See [Order Routing and Smart Order Routing](https://learn.tradelabsai.com/orders/order-routing/).

## How to judge your own execution

1. **Record the quote when you send an order** and compare it with your fill.
2. **Track slippage** on stops and market orders over many trades. See [Slippage Analysis](https://learn.tradelabsai.com/orders/slippage-analysis/).
3. **Check limit order fill rates:** how often do your limits fill when the price touches them?
4. **Compare total costs:** commissions plus spreads plus slippage, not commissions alone. See [All-In Trading Cost](https://learn.tradelabsai.com/orders/all-in-trading-cost/).
5. **Read your broker's routing and execution quality reports.**

## Best execution for institutions

Funds measure execution against benchmarks such as the arrival price, VWAP or the closing price, and report the results to clients. The broadest measure, [Implementation Shortfall](https://learn.tradelabsai.com/orders/implementation-shortfall/), compares the actual result with the price at the moment the decision to trade was made, capturing delay, market impact and missed trades.

## What it does not mean

- It does not mean every order fills at the best price ever seen that day.
- It does not cover your choice of order type. A market order in a thin market can be executed "best" by the rules and still be expensive.
- It does not remove the need for your own judgement about when and how to trade.

## Frequently asked questions

### What is best execution?

A broker's duty to seek the most favourable terms reasonably available for a customer's order, considering price, speed, likelihood of execution, size and cost.

### Does commission free trading mean worse execution?

Not necessarily, but it can. Commission free brokers often earn from order flow, so compare price improvement and execution quality, not just commissions.

### How can I tell if my broker gives good execution?

Compare your fills with the quotes at the time of your orders, track slippage, and review the broker's published routing and execution quality reports.

## Sources

- FINRA, [Rule 5310: Best execution and interpositioning](https://www.finra.org/rules-guidance/rulebooks/finra-rules/5310)
- Wikipedia, [Best execution](https://en.wikipedia.org/wiki/Best_execution)

## Continue learning

- Next lesson: [Fill Probability and Queue Position](https://learn.tradelabsai.com/orders/queue-position/)
- Previous lesson: [Execution Reports and Trade Confirmations](https://learn.tradelabsai.com/orders/trade-confirmations/)
- Related: [Execution Reports and Trade Confirmations](https://learn.tradelabsai.com/orders/trade-confirmations/): After you trade, you receive order acknowledgments, execution reports and a trade confirmation. Learn what each one shows and how to use them to check your fills.
- Related: [Order Routing and Smart Order Routing](https://learn.tradelabsai.com/orders/order-routing/): Order routing decides which venue your order is sent to. Learn how brokers route orders, smart order routers, payment for order flow and how routing affects fills.
- Related: [Slippage Analysis](https://learn.tradelabsai.com/orders/slippage-analysis/): Slippage analysis compares your fills with benchmark prices to measure execution quality. Learn the benchmarks, the formula and how to act on results.
- Related: [Implementation Shortfall](https://learn.tradelabsai.com/orders/implementation-shortfall/): Implementation shortfall compares a paper portfolio traded at the decision price with what you actually achieved. Learn the formula and its parts.
- Related: [How to Choose a Broker](https://learn.tradelabsai.com/industry/how-to-choose-a-broker/): A practical checklist for choosing a broker: regulation, safety of funds, real trading costs, markets, platforms, support and the red flags to watch for.