How a Stock Exchange Works

How a Stock Exchange Works
How a Stock Exchange Works
Table of Contents

Key Summary

What actually happens between clicking “Buy” and seeing the security appear in your portfolio? This overview explains the key principles of stock exchange trading: how a stock exchange works, how prices are formed, when trading takes place, which order types are available, and which costs may arise.

  • A stock exchange matches buy and sell orders under defined rules. 
  • Prices are formed by supply and demand in the order book. 
  • Price priority applies before time priority. 
  • A trading day includes opening and closing auctions and continuous trading. 
  • Order type, fees, spread, and liquidity affect trading.

The Swiss Stock Exchange Explained Simply

The Function of a Stock Exchange

A stock exchange is an organized, now largely electronic marketplace for securities such as shares, bonds, and exchange-traded funds (ETFs). Banks and brokers submit their clients’ orders to the trading system. The system matches compatible buy and sell orders according to a consistent set of rules.

The stock exchange does not set prices itself. It provides the infrastructure in which prices are formed transparently and transactions can be executed in a traceable manner. Listing, trading, and market supervision rules provide a reliable framework.

Price Formation and the Order Book

The price of a security is determined by supply and demand. In the electronic order book, buy orders are placed on one side and sell orders on the other. When the price and quantity match, the trading system automatically brings the corresponding orders together.

Orders with the best price generally receive priority. If prices are identical, the time at which the order was entered usually determines priority. This price-time priority makes execution transparent. The displayed price reflects the most recent transaction and can change continuously as new buy and sell orders enter the market.

Trading Hours and Trading Phases

A trading day consists of more than continuous trading. Before the market opens, the system collects orders without executing them. The opening auction then determines an initial price at which the largest possible number of orders can be matched. Continuous trading follows, and a closing auction determines the official closing price at the end of the day.

The exact times and processes vary depending on the trading segment and security. Trading interruptions and public holidays can also affect the regular schedule.

Order Types

The order type allows investors to specify the conditions under which a purchase or sale should be executed. A market order prioritizes rapid execution at the best available market price. A limit order, by contrast, sets a maximum purchase price or a minimum sale price. Stop orders become active only when a specified price is reached.

The choice of order type primarily affects the balance between price control and execution certainty. Not every trading venue offers the same additional order parameters, and more complex options are generally not necessary for beginners.

Stock Exchange Trading Costs

Various costs may arise when securities are bought and sold. Banks and brokers often charge a transaction fee or brokerage fee. Depending on the transaction, statutory charges such as Swiss transfer stamp tax may also apply. If securities are traded in another currency, currency conversion costs may be incurred as well.

In addition to directly disclosed fees, the spread also affects the effective trading costs: the wider the difference between the buy and sell prices, the less favorable the entry or exit price may be. Funds and ETFs may also involve ongoing product costs or custody fees. The costs that actually apply depend on the security, the trading venue, and the financial services provider selected.

Liquidity and the Spread

A liquid market has many buy and sell orders. As a result, securities can generally be traded more quickly without a single order having a significant impact on the price. The spread, which is the difference between the highest buy price and the lowest sell price, is an important indicator of liquidity.

The narrower the spread, the closer the price expectations of buyers and sellers. For less frequently traded securities, the spread may be wider, meaning that even a smaller order can have a greater impact on the execution price.

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