Learn the core rules of US stock trading, including T+1 settlement, dividend withholding tax, trading hours, order types, circuit breakers and key differences from Hong Kong stocks before entering the US market.
Basic Institutional Framework of US Stock Trading
Want to invest in world-leading companies such as Apple and Nvidia, but feel unfamiliar with US stock trading rules? Often hear about T+1 settlement and 30% dividend tax, but are unsure what they actually mean? This article clearly explains the core rules of US stock trading and directly compares the key differences with Hong Kong stocks, helping investors connect with international markets smoothly and take the first step into US stock investing with confidence.
Understanding the Five Key Differences Between US Stocks and Hong Kong Stocks Is the First Task for Beginners
These two major markets differ significantly in trading units, daily price limits, trading hours, settlement systems and stock tickers. Mastering these core differences can effectively prevent misunderstandings when placing orders. The following table provides a systematic comparison of five key rules:
| Comparison Item | US Stock Rules | Hong Kong Stock Rules | Meaning for Traders |
|---|---|---|---|
| Trading unit | The minimum unit is one share | Trades are made in board lots, with the number of shares per lot varying by company, such as 100 shares or 500 shares | The entry threshold for investing in high-priced US stocks is relatively lower |
| Daily price limits | No single-day price limit, but circuit breaker mechanisms are in place | No explicit daily limit-up or limit-down system | Single-day volatility in US stocks may be more intense, so circuit breaker rules should be monitored |
| Trading hours | Continuous intraday trading without a lunch break, with additional pre-market and after-hours sessions | Divided into morning and afternoon trading sessions, with a lunch break in between | News-driven volatility during US pre-market and after-hours trading requires extra attention |
| Settlement system | T+1 settlement, officially implemented from 28 May 2024 | T+0 trading system, allowing funds to be turned over multiple times on the same day | Hong Kong stocks have relatively higher fund turnover efficiency |
| Stock ticker | English abbreviations, such as AAPL and NVDA, related to company names | Five-digit numbers beginning with 0, such as Tencent Holdings 00700 | US stock tickers are more intuitive and easier to remember |
Daily Price Limits and Circuit Breaker Mechanisms
The US stock market has no single-day price limit, which means share prices may rise or fall by more than 20% or even more within one day. This high volatility brings higher potential returns, but also higher risk. To deal with extreme market conditions, the US market has market-wide circuit breaker mechanisms. If the S&P 500 Index falls by 7% in a single day, triggering Level 1, or by 13%, triggering Level 2, and this occurs before a specified time before the close, market-wide trading will be halted for 15 minutes. If the decline reaches 20%, triggering Level 3, trading will be halted for the rest of the day. By comparison, although Hong Kong stocks do not have an explicit daily limit-up or limit-down system, share prices may still fluctuate sharply due to news and other factors.
Trading Hours: No Intraday Break, Plus Pre-Market and After-Hours Trading
Regular US stock trading hours are continuous, with no lunch break. In addition, there are “pre-market” and “after-hours” trading sessions. Many major earnings releases or company announcements are published during these two sessions, causing sharp share price movements and giving investors longer trading hours and more trading opportunities. Because the United States observes daylight saving time, regular trading hours converted into Beijing time differ between summer time and winter time:
Summer time, approximately from mid-March to early November: 09:30 to 16:00 Eastern Time, corresponding to approximately 21:30 to 04:00 the next day Beijing time.
Winter time, approximately from early November to mid-March: 09:30 to 16:00 Eastern Time, corresponding to approximately 22:30 to 05:00 the next day Beijing time.
Hong Kong stock trading hours are divided into morning and afternoon sessions, usually from 09:30 to 12:00 in the morning and from 13:30 to 16:00 in the afternoon.
Understanding US Stock Cash Flows: Fees and Tax Rules Explained
In addition to trading rules, fees and taxes are key factors affecting investment returns. For overseas investors in particular, understanding the rules on dividend tax is essential.
Trading Fees: Comparing Sub-Brokerage and Overseas Brokers
There are two main channels for investing in US stocks: sub-brokerage through domestic brokers and directly opening an overseas brokerage account. Sub-brokerage fees are usually higher, but funds do not need to leave the investor’s jurisdiction and the operating process is similar to Hong Kong stock trading. Overseas brokers offer low or even zero commission, but require international wire transfers, and funds are regulated under overseas rules. Investors can choose according to their capital size and trading habits.
Dividend Tax: What Does the 30% Withholding Tax for Foreign Investors Mean?
This is the tax rule that non-US investors are most concerned about. When investors hold US stocks that pay dividends, the broker will withhold 30% dividend tax in advance. For example, if an investor receives a dividend of US$100, the actual credited amount will be US$70. This is the standard US tax rate for foreign investors, unless the investor’s country has a special tax treaty with the United States.
Capital Gains Tax: Do Profits From Buying and Selling Shares Need to Be Taxed?
For non-US overseas investors, gains from buying and selling US stocks, namely capital gains, are exempt from US tax. Investors do not need to report or pay tax on such gains to the United States, which is one of the reasons US stocks are highly attractive to global investors.
Essential US Market Rules Beginners Should Know Before Placing Orders
Before actually placing orders, becoming familiar with the market’s infrastructure and rules can make trading smoother. Investors can first open a demo account to practise and become familiar with the order placement process.
The Three Major US Exchanges
NYSENew York Stock Exchange: The oldest exchange, mostly listing large, mature blue-chip stocks such as Berkshire Hathaway and Coca-Cola.
Nasdaq Stock Market: The world’s largest electronic exchange, known for technology stocks such as Apple, Microsoft and Amazon.
AMEXAmerican Stock Exchange: Mainly trades shares of small and medium-sized companies and ETFs.
Understanding Common Order Types
Mastering basic order types is the foundation for effectively executing trading strategies:
Market order: Executed immediately at the best available market price, ensuring execution but not guaranteeing the price.
Limit order: Specifies a buy or sell price and is executed only when the market price reaches or improves on the specified price.
Stop-loss order: Sets a trigger price in advance. When the market price reaches that level, the order is automatically submitted as a market order and is commonly used to control losses.
Recent Real-World Event: Global Settlement Systems Are Accelerating Towards T+1
The implementation of the T+1 settlement system for US stocks is prompting major global markets to accelerate similar reforms. The following is a summary of a real-world event closely related to settlement systems:
Cause: On 28 May 2024, the US Securities and Exchange Commission officially shortened the standard settlement cycle for US stocks from T+2 to T+1. This move was viewed as a key step in reducing settlement risk and improving market efficiency, and it also set a reference standard for other markets.
Development: The European Union and the United Kingdom have successively announced a transition to T+1 settlement, with a unified conversion date scheduled for 11 October 2027. Relevant industry committees published testing plans and best practice guidance during 2026, while markets such as Turkey and South Africa are also evaluating or advancing similar transitions. (Source: BofA Securities, Global Accelerated T+1 Settlement market update report)
Impact: This trend means that global securities settlement efficiency is continuing to improve. Cross-market investors may face new coordination challenges in fund turnover and risk management in the future, but over the long term this should help reduce counterparty risk and also reflects regulators’ continued exploration of faster settlement cycles, or even future T+0 settlement.
Frequently Asked Questions About US Stock Trading Rules
What Is the Minimum Amount Needed to Invest in US Stocks? Can Investors Buy Just One Share?
Yes. The minimum trading unit for US stocks is one share, so the minimum investment amount is the price of one share of the stock an investor wants to buy. For example, if a stock is priced at US$50, only US$50, excluding fees, is needed to become a shareholder of that company.
Can US Stocks Be Bought and Sold on the Same Day?
Yes. US stocks allow day trading, meaning the same stock can be bought and sold within the same trading day. However, investors should note that if account assets are below US$25,000 and more than three day trades are made within five consecutive trading days, the account may be marked as a “Pattern Day Trader” and become subject to trading restrictions.
Can the 30% Tax Withheld From US Stock Dividends Be Reclaimed?
For most investors, this 30% withholding tax cannot be refunded. For example, Hong Kong and the United States have not signed a comprehensive tax treaty to reduce the dividend tax rate. This tax is deducted directly by the broker when dividends are paid, and investors do not need to file a separate return.
Do US Stocks Have So-Called “Warning Stocks” or “Designated Stocks”?
US stocks do not have a system similar to Hong Kong’s “warning stocks” or “designated stocks”. Even if a share price fluctuates sharply in the short term, the trading method will not be restricted. However, the US stock market has circuit breaker mechanisms, and trading will be halted to cool market sentiment when the overall market or individual stocks experience extreme volatility.
What Is the Pattern Day Trader Restriction?
If an account’s net value is below US$25,000 and more than three day trades are made within five consecutive trading days, the account will be marked by the system as a Pattern Day Trader. Subsequent day trading permissions may be restricted, so investors should pay attention to this rule to avoid limitations on account functions.
