Best Execution
Best execution is a broker’s obligation to seek the most favourable terms reasonably available for a client’s order, considering price, speed, likelihood of execution and costs. The precise rules differ by jurisdiction.
Best execution is the duty brokers owe clients when handling their orders: seek the most favourable terms reasonably available, not just the quickest fill. The detailed rules differ by country and regulator.
- Category
- Market Structure
- Reading time
- 4 min
- Also called
- Best execution obligation, Duty of best execution
- Updated
Best execution in plain words
In the US, FINRA Rule 5310 requires brokers to make a real effort to find the best market for each order, so the customer gets the most favourable price available at the time.1
In the EU, MiFID II requires firms to take every sufficient step to get clients the best overall result, weighing price, costs, speed, the chance of execution and settlement, order size and any other relevant factor.2
Price matters most for retail clients, but it is not the only factor — and the rules differ by jurisdiction.
How a broker meets best execution
Assess the market
Consider the market for the security: its price, volatility and liquidity, and how fast information moves.1
Consider the order
Another factor is the size and type of transaction.1
Compare venues
Check exchanges, market makers and other venues for the best terms.
Avoid conflicts
Payments for order flow and other routing incentives must never override the duty to get the best result.3
Watch fees
A venue's fees or rebates should not be what decides where an order goes.3
Review regularly
Brokers must review the quality of their executions regularly and in depth.1
Worked examples
Example 1 — Price improvement
Improved fillA hypothetical stock is quoted 10.00 bid / 10.02 ask. A buy order for 500 shares fills at 10.01.
| Saved per share | 0.01 |
| Total saved | 5.00 |
The duty is about the outcome: the best price reasonably available in the conditions at the time.1
Example 2 — Cheap fee, worse price
Net −9.50Venue A charges 0.50 less in fees but fills 1,000 shares 0.01 worse.
| Fee saving | 0.50 |
| Price cost | 10.00 |
The rebate made the route attractive to the broker, but the client's total result was worse — exactly what the rules forbid.3
Example 3 — Large order
Size changes the answerA hypothetical order is ten times the usual size at the best quote.
| Split | Several venues |
Because the size and type of transaction is a factor, working the order carefully can beat a single market order.1
US vs EU approach
| Aspect | US (FINRA 5310) | EU (MiFID II) |
|---|---|---|
| Standard | Reasonable diligence | All sufficient steps |
| Main focus | Price to customer | Total result, several factors |
| Reviews | Regular and rigorous | Monitoring of execution policy |
| Applies to | Broker-dealers | Investment firms |
Where best execution matters
Choosing a broker
Compare how a Broker routes orders.
Order types
When a Market Order or Limit Order fits.
Costs
Total cost beyond Trading Fees and Commissions.
Execution quality
Measuring Slippage and Bid-Ask Spread.
Advantages and disadvantages
Advantages
- Protects clients from poor fills.
- Pushes brokers to compare venues.
- Limits conflicts such as payment for order flow.
- Requires regular review of execution quality.
Disadvantages
- Rules differ by jurisdiction.
- Hard for clients to verify.
- Allows judgement, so outcomes vary.
- Does not guarantee the best price on every trade.
Going deeper
Read as far as you need. Each level builds on the one before it.
Not just price
Beginner
Price is only one factor; costs, speed, the chance of execution and settlement, order size and type all count.2
Cannot be outsourced
Intermediate
A broker cannot hand its best-execution duty to someone else, even when another firm actually handles the order.1
Conflicts
Advanced
For zero-commission brokers, the key question is whether payment for order flow is hurting clients' execution quality.3
Common mistakes
Equating zero commission with best execution
Price quality matters too.
Ignoring spread
Check fills against the quote.
Assuming one rule worldwide
Rules differ by country.
Never reviewing fills
Compare your fills over time.
Check your understanding
Test yourself before moving on. Each answer comes with an explanation.
Key points to remember
- Brokers must seek the best terms reasonably available.
- Price, costs, speed and likelihood all count.
- Payment for order flow must not override it.
- Firms must review execution quality regularly.
- Rules differ by jurisdiction.
Frequently asked questions
Does best execution mean the best price?
Do the rules apply to crypto?
How can I check my broker?
Further learning
- Broker
Who executes your orders.
- Slippage
Measuring execution cost.
- Bid-Ask Spread
The basic cost of trading.
- Market Maker
Who fills many retail orders.
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.
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.