Broker-Dealers, Traders & Clearing Firms

The six participants (roles)

In general, there are six participants (roles) you’ll want to recognize in the securities markets:

1. Traders
2. Broker-dealers
3. Introducing brokers
4. Clearing brokers
5. Clearinghouses
6. Market makers

🔑 Roles table — every role named on this page

Traders

• Traders are natural persons (human beings) or entities (businesses or organizations) that buy and sell securities on behalf of their clients.
• In practice, traders usually don’t speak with clients or maintain client relationships.
• Example: many mutual funds employ traders to carry out the fund’s objectives (e.g., a large-cap stock fund investing customer money into large-cap stocks). The fund manager sets the overall investment strategy, and the traders implement it by buying and selling securities for the fund.
• Traders working for large portfolios (like mutual funds) generally don’t have direct relationships with the investors in those portfolios.

Broker-dealers

• Broker-dealers are financial organizations that help customers buy and sell securities.

Five of the largest broker-dealers (in 2025), per the text:

What you know at execution

Assume you place a trade with your broker-dealer to buy shares of stock. When the trade executes, the transaction is locked in. At that point, you know:

• How many shares you purchased
• The price paid
• Any applicable transaction fees

After execution, additional steps happen behind the scenes to settle (finalize) the transaction. The exact steps depend on the type of broker-dealer handling the trade.

Introducing brokers

• Broker-dealers categorized as introducing brokers are often smaller firms that focus on customer relationships and trade facilitation.
• 🔑 Introducing brokers don’t maintain custody of customer assets, meaning they don’t keep possession of customer securities.
• Maintaining custody requires sophisticated technology and comes with strict recordkeeping requirements.
• 🔑 Introducing brokers also don’t process their customers’ trades. Instead, they outsource these responsibilities to clearing brokers.

Worked example (ABC / XYZ)

Clearing brokers

Many large broker-dealers are categorized as clearing brokers. These are broker-dealers that maintain custody, process orders, provide clearing services, and facilitate trades for:

• Their own customers, and

• The customers of introducing brokers

• Clearing services involve clearing brokers working with clearinghouses to ensure a transaction will occur. Clearing brokers act as intermediaries between their customers (including introducing brokers) and clearinghouses.

• Clearing brokers must be properly connected to the financial markets to process orders.

• Many securities trade in more than one market (often through multiple market makers). If a stock is trading in five different markets, the clearing broker is responsible for finding the market that can execute the trade efficiently at the best price.

Clearinghouses

• A clearinghouse is an organization responsible for making sure trades are properly finalized.
• As an investor, you generally don’t have to worry that a transaction will fail because one side doesn’t deliver what they owe.

Example of the clearinghouse guarantee

Assume an investor sells stock at $50, but the buyer doesn’t deliver the required cash. Clearinghouses operate behind the scenes to prevent this from becoming the seller’s problem. The mechanics are more complicated than this, but the basic idea is that a clearinghouse would pay the seller out of its own pocket and then work with the buyer’s broker-dealer to be reimbursed.

• This kind of system is essential for confidence in the financial markets. Would you place a trade if you thought the contra-party (the other side of the transaction) might not follow through?

🔑 Clearinghouses are responsible for ensuring:

• The buyer receives the security, and
• The seller receives the cash

What happens when a trade finalizes

Sidenote — Settlement

• Several protocols are followed behind the scenes after a trade executes. That’s why settlement takes time, even in today’s digital age.

Market makers

• Market makers are organizations that buy and sell securities solely on a principal basis (with inventory) to traders, broker-dealers, and other public customers.
• They maintain ongoing bid & ask spreads and provide liquidity for the securities they trade.
• Most market makers are registered as broker-dealers — in particular, clearing brokers.

The pineapple stand analogy

Assume you have a large inventory of pineapples. You put a pineapple stand in front of your house with a sign that said: “I will trade pineapples with anyone! You can sell me one for $2, or you can buy one for $3.”

• Now replace pineapples with securities. Market makers buy and sell securities with the public and profit from doing so. They post bid and ask prices, which allows them to earn a spread while adding liquidity to the market.
• Broker-dealers route customer trades to market makers (typically those offering the best prices), and the market makers fill those orders.
• Because traders and broker-dealers look for the best available price to maximize client returns, market makers with better prices tend to execute more trades.

Sidenote — Payment for order flow (PFOF)

• Many market makers engage in payment for order flow (PFOF), which compensates broker-dealers and other institutions for customer order traffic.

The pineapple version of PFOF

Assume there’s a $2 bid, $3 ask, and a $1 spread.

As a pineapple market maker, you build relationships. One relationship is with a pineapple broker-dealer that has many customers who regularly trade pineapples. You don’t know those customers, but you want their order flow. You make a $1 profit from every pineapple traded.

You and the pineapple broker-dealer enter a revenue-sharing agreement. For every full pineapple trade you complete for their customers (buy a pineapple from one customer at $2, sell to another customer at $3), you share half your profits ($0.50). Your profit per trade is smaller, but you may earn more overall because the broker-dealer sends many trades your way.

• Replace pineapples with a security like common stock, and you have PFOF.
• Today, it’s common for market makers to use PFOF with financial institutions, especially large discount brokers like Robinhood, TD Ameritrade, Charles Schwab, and E-Trade. These organizations send client trade requests to specific market makers in return for compensation.
• 🔑 PFOF is one of the primary reasons firms like these can avoid charging commissions.

Best execution

• Broker-dealers are subject to best execution standards, which require routing customer orders to the venue or market maker offering “best execution.”
• The definition of best execution is debated in the securities markets and has been subject to ongoing review by the Securities and Exchange Commission (SEC); a formal rulemaking proposal under the prior SEC administration was not adopted.
• The key question is whether firms prioritize customers or the market makers paying them, especially since “best execution” can be interpreted in different ways.

🔑 The SEC currently defines best execution as:

The duty of best execution requires a broker-dealer to execute customers’ trades at the most favorable terms reasonably available under the circumstances.

Arguments for and against PFOF

• Some studies show investors (especially retail investors) can be negatively impacted by PFOF, but typically only by a few pennies or less per share traded.

Example: a broker-dealer routes a customer’s stock purchase to MM1 (market maker 1) because MM1 pays PFOF, even though MM2 would have executed the same trade for $0.01 less per share but pays no PFOF.

Real-world case — Robinhood (2020)

Key points

Broker-dealers

• Facilitate and perform securities transactions for customers

Introducing broker

• Broker-dealer that facilitates trades for customers
• Does not maintain custody, process orders, or provide clearing services
• Hires a clearing broker to perform the actions above

Clearing broker

• Broker-dealer that maintains custody, processes orders
• Acts as an intermediary (clearing service) between investors and clearinghouses

Clearinghouse

• Organization responsible for clearing trades
• Ensures buyers deliver cash
• Ensures sellers deliver securities

Settlement rules

• Most securities:
  • One business day after the trade (T+1)

Market makers

• Buy and sell securities with the public
• Acts only in a principal (dealer) capacity

Payment for order flow

• Broker-dealers paid to send customer orders to market makers
• Broker-dealers must abide by ‘best execution’ standards

Sources

Primary/official references for the material in this chapter. Every link was fetched and returned HTTP 200 on 2026-08-15.