How does the stock market work? One order from tap to settlement

A stock trade looks instant on a phone, but at least four organizations handle it before the shares are yours: your broker, the venue that fills the order, the clearing house NSCC and the depository DTC. The US market is a web of competing venues held together by SEC rules on price, reporting and settlement. This guide explains each player and the National Best Bid and Offer that ties them together, then follows one order through the whole chain with timestamps.

Where do stock trades actually happen?

US stock trades happen on 18 stock exchanges and, for nearly half of all volume, away from exchanges at wholesalers and alternative trading systems. Cboe's market volume summary for Friday, October 30, 2026 shows how that day's 20.3 billion shares split.

The SEC's list of registered national securities exchanges has 29 names, but several of them trade only options. A listing does not confine a stock to one exchange: Nasdaq-listed shares trade on NYSE Arca and IEX, and NYSE-listed shares trade on Nasdaq's markets. The listing exchange matters mainly for its listing standards and for the opening and closing auctions that set each stock's official prices.

Off-exchange volume comes from two kinds of venue. Alternative trading systems are matching engines run by broker-dealers under the SEC's Regulation ATS, and those that trade listed stocks must publish a detailed Form ATS-N on the SEC's website; the ones that hide their orders until they trade are often called dark pools. Wholesalers are large market makers that fill orders from retail brokers against their own inventory. Both report every trade to a FINRA trade reporting facility rather than to an exchange.

What do market makers and wholesalers do?

Market makers quote a bid and an offer all day and earn the spread; wholesalers are market makers that fill many retail orders away from exchanges. Without market makers, a buyer would often have to wait for a seller to show up at a matching price.

A market maker on an exchange posts quotes that anyone can trade against. A wholesaler works differently: retail brokers send it their customers' orders directly, and it decides whether to fill them from its own inventory, often at a price slightly better than the best quote on display. Investor.gov calls that price improvement "the opportunity, but not the guarantee" of a better price than the current quote. That order flow is valuable to the wholesaler, so some wholesalers pay brokers for it: perhaps a penny or more per share, in Investor.gov's description of payment for order flow.

That payment is legal and disclosed. In June 2025 the SEC withdrew its 2022 order competition proposal, which would have exposed many retail orders to auctions before a wholesaler could fill them. Brokers publish quarterly Rule 606 reports showing where they sent orders and what they were paid, and from August 1, 2026 amended Rule 605 requires brokers with large numbers of customers, not only market centers, to publish monthly execution-quality statistics, including a short summary report.

How does your broker decide where to send an order?

Your broker's routing system chooses a venue for each order under a duty of best execution: seeking the most favorable terms reasonably available for that order. Speed, price, the chance of a fill and cost all count.

Investor.gov lists the usual destinations: the exchange that lists the stock, another exchange, a market maker or wholesaler, an electronic communications network, or the broker's own inventory, which is called internalization. Brokers judge execution quality across all their customers' orders in aggregate rather than one order at a time, and they review the venues periodically. In practice, small orders that can trade at once are often sent to wholesalers, while limit orders priced away from the market may be routed to exchanges to wait in the order book.

The SEC sets no deadline for executing an order, but a firm that advertises its speed must not exaggerate it. Whether your order can trade at once depends on its type and limit price, which stock order types explains in depth.

What is the National Best Bid and Offer?

The National Best Bid and Offer is the highest displayed bid and the lowest displayed offer for a stock across all exchanges, recalculated continuously from each exchange's best quote. It is the benchmark every other venue is measured against.

Under Regulation NMS, trading centers must keep policies designed to prevent trade-throughs, which are trades at a price worse than a protected bid or offer displayed on another exchange. That is why a market buy order should not fill above the national best offer during regular hours, whether it executes on an exchange or at a wholesaler. The rule's definition covers regular trading hours only, one reason prices in the pre-market and after-hours sessions can stray from quotes elsewhere. On June 11, 2026 the SEC proposed rescinding this trade-through rule, Rule 611 of Regulation NMS, along with the rule on locked and crossed markets; a proposal does not take effect unless the Commission votes to adopt it.

Only round-lot quotes form the NBBO, and since November 3, 2025 a round lot depends on the stock's price: 100 shares for stocks priced up to $250.00, 40 shares from $250.01 to $1,000.00, 10 shares from $1,000.01 to $10,000.00, and 1 share above $10,000.00. Smaller odd-lot orders still trade, sometimes at better prices than the NBBO, but they do not set it. Quotes for stocks priced at $1 or more move in one-cent steps. The SEC has adopted a half-cent step for stocks with very narrow spreads and a cut in the cap on exchange access fees from 30 to 10 mils (from 0.3 to 0.1 cents) a share, but in June 2026 it delayed compliance with both to the first business day of November 2027.

What happens after your trade is executed?

The trade is reported to the public tape within seconds, cleared by the National Securities Clearing Corporation, and settled through the Depository Trust Company a business day later. Both NSCC and DTC are part of DTCC, the industry-owned post-trade utility.

Exchange trades go straight to the consolidated tape run by the securities information processors. Off-exchange trades must be reported to a FINRA trade reporting facility as soon as practicable and no later than 10 seconds after execution; reports that arrive later are marked late and do not update the last-sale price. Your broker must also send a confirmation at or before the completion of the trade, showing the date, the price, the number of shares, whether it acted as your agent or as principal, and whether it receives payment for order flow.

Clearing comes next. NSCC receives the trade details from the exchanges and FINRA facilities, and once a trade is validated it guarantees completion and steps in as buyer to every seller and seller to every buyer, a legal process called novation. Its continuous net settlement system then nets each member's buys and sells in each stock into a single daily delivery or receipt. DTCC reports a netting rate of 98.6% for the third quarter of 2026, so only about 1.4% of the gross value has to move, and members posted an average of about $18.3 billion in margin to back the guarantee.

Settlement is the exchange of shares for cash. The standard cycle for US stocks and ETFs: One business day after the trade (T+1), since May 28, 2024. On settlement day DTC moves the shares by book entry from the selling firm's account to the buying firm's, the cash moves through settlement banks, and no certificates change hands. Because the count uses banking days, a bank holiday on which stocks still trade, such as Veterans Day, pushes settlement back a day; the market hours and holidays page lists those dates. Secondary-market Treasury bills usually settle the next business day too, by market convention rather than under the stock rule, as how to buy Treasury bills explains.

What does one order look like from tap to settlement?

Here is one illustrative market order to buy 20 shares of a $50 stock, traced from the tap on a phone to settlement the next business day. The timings show typical orders of magnitude, not measurements from any one firm.

You can usually sell the shares as soon as the buy fills, before settlement. In a cash account, though, selling shares you have not yet paid for runs into the free-riding rule described in the stocks hub. For the full first-purchase walk-through, from funding an account to the order screen, see how to buy stocks.

Who regulates the stock market?

The SEC oversees the whole system, FINRA supervises brokers and off-exchange trading, and each exchange polices its own members under rules the SEC approves. Brokers that deal with the public must register with the SEC and join FINRA.

Exchanges and FINRA are self-regulatory organizations, so their rulebooks carry legal force once the SEC approves them. Orders, routes and trades in US stocks are also recorded in the Consolidated Audit Trail, which SEC staff drew on in 2026 to study overnight trading. You can look up a brokerage firm and its registered representatives on FINRA BrokerCheck.

The same rules include market-wide circuit breakers: a 7% (Level 1) or 13% (Level 2) fall in the S&P 500 from the prior day's close halts trading for 15 minutes if it happens before 3:25 p.m. ET, and a 20% fall (Level 3) ends trading for the rest of the day. SIPC, by contrast, is not a trading regulator. It steps in when a brokerage firm fails and customer assets are missing, covering up to $500,000 per customer, including up to $250,000 in cash, and it does not cover losses from falling prices; SIPC coverage and FDIC vs SIPC explain the limits.

What are the risks in how trades are executed?

The main execution risks are paying more than the quote you saw, trading when spreads are wide, and conflicts of interest in where your order is sent. Each can be managed once you know where it comes from.

• Quotes come with a size. A displayed offer covers a set number of shares, and a larger market order works up to worse prices, as in the 1,000-share NBBO example above.
• Prices move between tap and fill. In a fast market the best quote can change in milliseconds; a limit order sets the worst price you will accept.
• Wide spreads. Thinly traded stocks and extended sessions can have spreads of several cents or more, and you pay that gap on every round trip.
• Routing conflicts. Payment for order flow gives a broker an incentive that may not match yours. Rule 606 and Rule 605 reports let you compare where orders go and how well they fill.
• Halts and outages. An exchange can halt a single stock for pending news or a technical problem, and a market-wide halt stops all trading at once.
• Firm failure. NSCC's guarantee protects validated trades, and SIPC covers missing assets at a failed broker, but neither protects you from a falling share price.

The live pages for SPY and the other stocks we track show the latest trade price for each symbol, and how to read a stock quote explains every field around it. The stocks hub maps the rest of the basics.