How Stock Trading Works
Stock trading works by sending a buy or sell order through a broker, which arranges execution with another market participant. Once the trade executes, clearing and settlement complete the exchange of shares and money. The screen makes this look like one action, but placing an order, getting a fill and settling the transaction are separate events.
This guide follows that process for ordinary U.S. company shares. It focuses on the mechanics rather than stock selection; the broader stock trading guide covers the surrounding topics.
What You Buy When You Trade Stocks
A share represents part ownership of a company. Buying common stock gives you an economic interest in that business, usually with voting rights and eligibility for dividends if the company declares them. Neither dividends nor price gains are guaranteed, as the SEC explains in its overview of stock ownership and risks.
Ordinary exchange trading takes place in the secondary market for existing securities. You generally buy shares from another holder or market participant, not from the company itself. Your purchase money goes to the seller; the company does not receive fresh capital every time its stock changes hands.
Shares held through a brokerage account are commonly held in “street name.” You are the beneficial owner, while a broker or nominee appears in the registration chain. The SEC distinguishes this arrangement from holding shares directly as a registered owner. Buying through a broker does not, by itself, mean you are buying a derivative instead of shares.
How Stock Prices and Quotes Work
A stock does not have one permanently available purchase price. A quote normally includes a bid and an ask. The bid is the highest quoted buying price, while the ask is the lowest quoted selling price. The difference is the spread.
Suppose a hypothetical stock shows a bid of $49.98 and an ask of $50.02. The spread is $0.04 per share. If you bought 100 shares at that ask and immediately sold them at that unchanged bid, the difference would cost $4 before other charges. No unfavorable price movement is required.
The last traded price answers a different question: where did the most recent reported transaction happen? It does not promise the same price for your order. Quotes also apply to available quantities, so a large order might need several fills at different prices. The SEC’s explanation of trade execution describes why prices can change between submission and execution.
Prices move as participants change what they are willing to pay or accept. Company prospects, interest rates and economic conditions can influence those decisions, as FINRA explains when discussing stock performance. Every completed trade still has both a buyer and a seller; rising prices do not mean sellers have disappeared. For the company research behind those decisions, see fundamental analysis for stock traders.
Submitting an Order Through Your Broker
On an order ticket, you choose the account, stock symbol, buy or sell instruction, quantity, order type and duration. Review the company name as well as the symbol, and check whether the quantity represents shares or dollars. An order for 100 shares is not an order to spend $100.
Some brokers offer fractional shares, allowing you to invest a dollar amount rather than buy whole shares. At an assumed execution price of $200, a $50 purchase would buy 0.25 shares before fees. Availability, execution methods, permitted orders and transfer arrangements vary, as the SEC’s fractional share bulletin explains.
Choose how the order should execute
The order type tells the broker what matters: executing promptly, respecting a price boundary, or waiting for a trigger. FINRA’s order type guidance describes the main choices.
| Order | Instruction | Main risk |
|---|---|---|
| Market | Buy or sell at the available market prices. | The execution price can differ from the quote you saw. |
| Limit | Buy at the limit price or lower; sell at the limit price or higher. | Some or all of the order might remain unfilled. |
| Stop | Activate a market order when the stop is triggered. | The stop price is not a guaranteed execution price. |
| Stop limit | Activate a limit order when the stop is triggered. | The price restriction can prevent execution. |
A buy limit of $50 means “pay no more than $50 per share,” not “buy as soon as possible whatever the price.” A stop order also cannot guarantee a maximum loss. If the market jumps past its trigger, execution can occur at a worse price. Our stock order types guide covers these instructions in more detail.
Duration matters too. A day order expires after its applicable trading session if unfilled. A good till canceled order can remain active longer, although brokers impose expiration policies. FINRA’s guide to order durations and execution conditions explains these distinctions.
Your broker routes the order
The stock’s listing exchange is not necessarily where your transaction happens. A broker may route an order to an exchange, an electronic matching venue or a market maker that trades from its own inventory. Some orders are filled internally. Under the SEC’s execution guidance, brokers must seek the best execution reasonably available; routing involves more than sending every order to the same place.
A market maker may therefore take the other side of your trade. There does not need to be another individual clicking “sell” at precisely the moment you click “buy.”
Check whether the order actually filled
Submission is not execution. An accepted order may remain open, execute completely or receive a partial fill. If you request 20 shares and only 12 execute, you have bought 12 shares. The remaining eight are still subject to the order’s terms.
Check the execution quantity, average price and outstanding balance before placing another order. Cancellation is also a request, not a time machine: an order may execute before the cancellation reaches it. Fidelity’s order placement and cancellation guidance illustrates these distinctions, including why submitting a replacement does not automatically cancel the original.
What Happens During Clearing and Settlement?
Execution establishes the trade’s price and quantity. Clearing processes the resulting obligations between firms, and settlement completes delivery of the securities and payment. DTCC’s National Securities Clearing Corporation provides equities clearing and netting services, while its Depository Trust Company provides book entry securities settlement. Netting reduces the number of separate obligations firms must settle.
Most ordinary U.S. stock trades settle on T+1, one business day after execution. A Monday trade normally settles Tuesday; a Friday trade normally settles Monday, assuming no intervening settlement holiday. FINRA’s settlement cycle explanation distinguishes the trade date from the settlement date.
That distinction matters in a cash account. Buying power, settled cash and cash available to withdraw are not interchangeable balances. Do not assume that a sale showing in your transaction history makes its proceeds immediately available for every purpose.
For example, using unsettled sale proceeds to buy another stock and then selling that new holding before it has been paid for with settled funds can create a good faith violation. Conversely, a purchase fully funded with settled cash does not automatically require a one day holding period. Fidelity’s cash account examples show why the source of payment matters.
A Stock Trade Example: Purchase, Sale and Profit
Consider a hypothetical purchase of 20 shares in a cash account. Assume the order fills completely at $50.02 per share and the account already contains enough settled cash.
Purchase value: 20 × $50.02 = $1,000.40.
Later, you sell all 20 shares at an actual execution price of $53. The sale produces $1,060 before charges, giving a gross trading profit of $59.60. If total purchase and sale charges were $2, the profit would be $57.60 before tax. The $1,060 sale proceeds are not all profit; most of that amount is your original capital coming back.
If the sale instead executes at $47, proceeds are $940 and the loss is $60.40 before charges. These calculations use actual fills rather than a chart price or an intended exit price.
Ignoring dividends and other adjustments, the calculation is straightforward: multiply the difference between sale and purchase prices by the number of shares, then subtract trading costs. For tax reporting, use the applicable cost basis and reporting rules rather than assuming this simplified calculation covers every adjustment.
When Stock Trading Takes Place
The regular U.S. stock session runs from 9:30 a.m. to 4 p.m. Eastern Time on normal trading days, with holidays and some shortened sessions. Check the NYSE trading calendar and session hours rather than assuming every weekday follows the same schedule.
Some brokers offer premarket, after hours or overnight trading. Access depends on the broker, security and venue. FINRA warns that extended hours trading can involve lower liquidity, greater volatility and different order restrictions. A market order submitted while its eligible session is closed may wait for that session to reopen; it does not reserve the previous closing price.
Cash Accounts, Margin and Short Selling
In a cash account, you pay for purchases in full. A margin account permits borrowing against eligible account assets, subject to approval and requirements. Borrowing introduces interest costs and can produce losses greater than your cash contribution. The broker may also sell assets without consulting you first to address a margin deficiency. These risks are covered in the SEC’s margin account bulletin.
Selling shares you already own closes or reduces a long position. Short selling is different: it generally involves borrowing shares, selling them and later buying shares back to return to the lender. A falling price can produce a profit, while a rising price creates losses that are theoretically unbounded. The SEC explains the distinction between long stock purchases and short sales.
Neither borrowing nor short selling is necessary for an ordinary stock purchase. Confirm the account type and transaction instructions rather than treating extra buying power as extra savings.
Costs and Checks Before You Trade
A zero commission offer does not remove every cost. Spreads, execution differences, margin interest and applicable account or transaction fees still deserve attention. FINRA’s guidance for new investors recommends reviewing fees and the firm’s customer relationship summary. Our guide to choosing a stock broker covers the selection process separately.
In a taxable U.S. account, selling stock generally creates a capital gain or loss based on proceeds and adjusted basis. Holding periods affect its classification. The IRS guidance on capital gains and losses explains the basic framework; individual tax treatment can require further advice.
Before submitting an order, check four things:
- The company, symbol, account and buy or sell instruction are correct.
- The quantity and estimated total match what you intend to commit.
- The order type, price instructions and eligible session match your plan.
- You know how the purchase will be funded and how to check its status.
Keep the execution and settlement records afterward. Then judge the decision separately from whether the platform processed it correctly. Accurate execution cannot make a poor trade profitable; use a separate stock trading risk management plan to decide how much exposure you are prepared to take.