Market making works by having specialized trading firms post continuous buy and sell quotes on a security, standing ready to take the other side of your trade so you get immediate execution; the firm earns the small gap between its buy price and sell price, called the bid-ask spread, on each round trip. Those firms also collect exchange rebates for providing liquidity and, in the United States, often receive payments from retail brokerages in exchange for the right to fill their customers’ orders. Federal rules set floors on how fine the quoting increments can be, how consistently the firm must keep quotes live, and how close to the prevailing market those quotes must stay.
What a Market Maker Actually Does When You Trade
When you click sell on a brokerage app at 2:14 p.m., the other side of your trade is almost never another individual clicking buy at the same instant. A market maker steps in as the counterparty, taking your shares into its own inventory or selling you shares out of stock it already holds. The transaction clears in milliseconds. You get out of the position at a price close to the last trade, and the market maker now carries whatever risk comes with holding that inventory until the next order on the opposite side arrives.
That immediacy is what traders mean by liquidity. A liquid market lets you enter or exit without waiting for a natural match and without your order itself shoving the price around. Market makers create that environment by keeping standing orders on both sides of the order book throughout the trading day. Without them, thinly traded stocks would see long gaps between transactions, wild swings on small orders, and execution delays that would make active investing impractical.
Not every market maker carries the same duties. On most electronic exchanges, registered market makers must post two-sided quotes within a band of the national best price, but the obligations are relatively light. NYSE Designated Market Makers, or DMMs, operate under heavier requirements, including quoting at the national best bid or offer for a set percentage of the trading day and running the opening and closing auctions.1SEC.gov. NYSE DMM Quoting Requirements – Exhibit 52NYSE Data Insights. Market Making and the NYSE DMM Difference Electronic market makers on Nasdaq or Cboe face fewer manual duties but still have to keep continuous quotes live.
The Bid-Ask Spread Is the Core Profit Mechanism
Every market maker posts two prices: a bid (what it will pay to buy from you) and an ask (what it will charge to sell to you). The ask is always higher than the bid, and that gap is the spread. If the bid on a stock is $50.00 and the ask is $50.02, a round trip (buy at the ask, sell at the bid) costs you two cents per share. That two cents is the market maker’s gross compensation for standing in the middle.
The spread exists because the firm is accepting risk. Between the moment it buys from one customer and the moment it finds a buyer to sell to, the price can move. Tight spreads, sometimes as narrow as a penny, signal that a stock is heavily traded and the market maker faces little risk of getting stuck. Wide spreads on low-volume names reflect greater uncertainty. Watching the spread on a stock tells you more about real-time liquidity than almost any other single number.
How Tick Sizes Set the Floor
Federal rules dictate the smallest increment at which prices can be quoted, which effectively sets a floor on how narrow spreads can get. Under SEC Rule 612, stocks priced at $1.00 or above historically traded in one-penny increments. An amended version of that rule took effect in November 2025, introducing half-penny increments for certain stocks. If a stock’s time-weighted average quoted spread over the evaluation period was $0.015 or less, it now trades in $0.005 increments. All other stocks priced at $1.00 and above remain at $0.01 ticks, and stocks below $1.00 can be quoted in increments as fine as $0.0001.3eCFR. 17 CFR 242.612 – Minimum Pricing Increment
The half-penny tick matters because it lets market makers compete on price more granularly for the most liquid stocks. Before the change, two competing firms who both wanted to post a better quote had to jump a full penny, which sometimes made improving the quote unprofitable. Finer competition should translate into tighter spreads and lower costs for investors on heavily traded names.4SEC.gov. Tick Sizes – A Small Entity Compliance Guide
How Market Makers Manage Inventory Risk
Market makers don’t want to bet on where a stock is headed. They want to process volume and capture spreads. But the nature of the business means they inevitably accumulate directional exposure. If retail investors are net buyers of a stock all morning, the market maker ends up short. If they’re net sellers, the firm piles up long inventory. Either way, the firm now has a position that could lose money if the price moves against it.
Firms run automated systems that track net position across thousands of securities simultaneously. When inventory in any single name drifts beyond internal risk thresholds, the first response is usually to shift the quotes themselves: making the bid less attractive to discourage further buying, or sweetening the ask to attract sellers who will help offset the position. This is why spreads sometimes widen on a stock for no obvious news reason. The firm may simply be signaling that it’s overloaded.
For larger or stickier exposures, firms hedge using derivatives. A market maker sitting on excess long exposure in a tech stock might short an index future or buy put options to neutralize the directional risk. In options market making specifically, delta hedging with the underlying stock or index futures is the standard approach, though research shows that even professional options market makers don’t always maintain textbook-perfect hedges and rely heavily on active rebalancing of their options positions themselves.5Financial Management Association. Options Market Makers
The constant quote adjustment in response to order flow is also how markets discover price. A wave of buy orders pushes bids and asks up because the incoming demand suggests the stock might be underpriced. Sell pressure drags quotes down. With dozens of firms competing on the same stock, their overlapping quotes converge on a consensus price in microseconds.
The Three Ways Market Makers Make Money
The spread is the primary revenue source, but it isn’t the only one. The economics of modern market making rest on three channels, and the balance between them has shifted significantly over the past decade.
Spread Capture
The core business: buy at the bid, sell at the ask, pocket the difference. On a stock with a one-penny spread, the gross profit per share is a fraction of a cent after accounting for the risk of adverse price movement between trades. The economics only work at enormous scale. Major market making firms process billions of shares per day, and tiny per-share margins add up.
Exchange Rebates
Most U.S. equity exchanges operate on a maker-taker pricing model. When a market maker posts a resting limit order that another trader executes against, the exchange pays the market maker a small per-share rebate for making liquidity. The trader who takes the liquidity by executing against that resting order pays a fee. Cboe BZX, for example, pays a standard rebate of $0.0016 per share for displayed orders that add liquidity.6Cboe. Cboe BZX U.S. Equities Exchange Fee Schedule Rebates vary by exchange and often increase at higher volume tiers, with exchanges rewarding firms that bring more trading activity by offering better rates as a firm’s monthly share of total volume grows.7Federal Register. Volume-Based Exchange Transaction Pricing for NMS Stocks
Payment for Order Flow
In this arrangement, a wholesale market maker pays a retail brokerage a small fee, typically a fraction of a cent per share, in exchange for the right to execute that broker’s customer orders. The market maker profits by capturing the spread on a flow of orders that tends to be less informed, and therefore less risky, than institutional order flow. The brokerage uses the revenue to subsidize commission-free trading.8U.S. Securities and Exchange Commission. Special Study – Payment for Order Flow and Internalization in the Options Markets
Payment for order flow remains legal in the United States, though it has drawn sustained regulatory scrutiny. The SEC chairman has publicly discussed banning the practice, and the European Union agreed to phase it out by mid-2026. Australia, Canada, Singapore, and the United Kingdom have already banned it.9U.S. Securities and Exchange Commission. How Does Payment for Order Flow Influence Markets The practice creates an inherent tension: the broker has a financial incentive to route your order to whichever market maker pays the most, which may not be the one offering the best execution.
Price Improvement and What You Actually Pay
Wholesale market makers that receive order flow often execute trades at prices slightly better than the publicly displayed best bid or offer. If the national best offer on a stock is $50.10, the wholesaler might fill your buy order at $50.098, saving you a fraction of a cent per share. This is called price improvement, and it’s the main argument market makers use to justify payment for order flow. The overall cost to the investor, they say, is lower than it would be on a public exchange even after accounting for the payment to the broker. Wholesale market makers have reported improving prices on over 90 percent of small orders in S&P 500 stocks.
The counterargument is that price improvement is measured against the displayed quote, which might itself be wider than it would be without PFOF. If more retail orders hit public exchanges instead of being routed to wholesalers, the increased competition could tighten displayed spreads for everyone.
Regardless of where that debate lands, all broker-dealers face a legal obligation to seek the best available execution for customer orders. FINRA Rule 5310 requires firms to use reasonable diligence to find the best market for a security, considering factors like price, volatility, liquidity, order size, and the terms of the order.10FINRA. 5310 – Best Execution and Interpositioning Best execution doesn’t require the absolute best price on every trade, but it does mean the broker can’t systematically sacrifice execution quality for routing kickbacks.
The Rules That Keep Market Making Honest
A firm that controls both sides of the order book has substantial power to influence prices if left unchecked. Several SEC and FINRA rules constrain how market makers operate.
Order Routing Disclosure
SEC Rule 606 requires every broker-dealer to publish quarterly reports detailing where it routes customer orders, the net payments received from or paid to each venue, and a description of any payment for order flow or profit-sharing arrangements. These reports break down routing by order type (market orders, marketable limit orders, and non-marketable limit orders) and must stay publicly accessible on the broker’s website for three years.11GovInfo. 17 CFR 242.606 – Disclosure of Order Routing Information If you want to see whether your broker routes your trades to the highest PFOF bidder, the Rule 606 report is where to check.
Continuous Quoting Obligations
Firms designated as Lead Market Makers or DMMs must maintain continuous two-sided quotes during the trading day. On NYSE Arca, Lead Market Makers must keep displayed limit orders on both sides of the market throughout the core trading session.12NYSE Arca. NYSE Arca Lead Market Maker Performance Requirements Standard registered market makers on other exchanges face similar but looser requirements, typically needing to quote within 8 to 30 percent of the national best price.2NYSE Data Insights. Market Making and the NYSE DMM Difference Failing to maintain these quotes can draw FINRA fines or loss of market-making privileges, with penalties ranging from tens of thousands of dollars into six-figure territory depending on scope and duration.
The Stub Quote Ban
Before 2010, market makers could technically satisfy their quoting obligations by posting absurd prices, offering to buy a $50 stock at $0.01 or sell it at $100,000. These “stub quotes” existed solely to check the regulatory box without providing real liquidity. During the May 2010 flash crash, some stocks traded at these stub prices when legitimate quotes disappeared, causing brief but spectacular price dislocations. The SEC prohibited stub quotes effective December 2010. Market makers in securities covered by the circuit breaker program must now maintain quotes within 8 percent of the national best bid or offer during regular hours, with a wider 20 percent band near the open and close. For securities outside the circuit breaker program, quotes must stay within 30 percent. In each case, a quote can drift an additional 1.5 percent before the firm must enter a new one within the required band.13U.S. Securities and Exchange Commission. SEC Approves New Rules Prohibiting Market Maker Stub Quotes
Short Selling Exemption
Market makers receive a notable exemption from Regulation SHO’s locate requirement for short sales. Normally, a broker must borrow shares or have reasonable grounds to believe shares can be borrowed before executing a short sale. Market makers engaged in bona fide market making are exempt because their role requires selling shares they may not currently own when absorbing buy orders.14eCFR. 17 CFR Part 242 – Regulation SHO – Regulation of Short Sales The exemption only applies to genuine market making activity. A firm can’t claim it while running a directional trading strategy under the guise of market making.
Wash Sales and Self-Trading
Because market makers operate on both sides of the order book, there’s a risk that their own buy and sell orders match against each other, creating trades that involve no real change of ownership. FINRA Rule 5210 requires that all reported transactions be bona fide, and firms must maintain policies designed to prevent a pattern of self-trades originating from the same algorithm or trading desk.15Federal Register. Self-Regulatory Organizations – FINRA – Notice of Filing Relating to Wash Sale Transactions and FINRA Rule 5210 Isolated accidental self-trades don’t trigger violations, but a persistent pattern does, particularly when it accounts for a material percentage of volume in a given security.