The Zero-Commission Era in U.S. Equity Trading: The Truth Behind "Free" Trades

TL;DR: “Zero-commission” U.S. stock trading is not cost-free—trading commissions are only one part of the overall cost. Platform fees, FX conversion spreads, dividend withholding tax, and regulatory charges can all affect your actual returns. This article breaks down each fee to help Hong Kong investors calculate their true trading costs and make smarter investment choices.

In recent years, the idea of “zero-commission U.S. stocks” has swept through the online brokerage market, attracting more and more Hong Kong investors to trade U.S. equities on their own. Many advertisements use “zero commission” as a hook; however, once investors start calculating the real expenses of each trade, they often discover a long list of fees hiding behind the word “free.”

Understanding the overall cost structure of U.S. stock trading is an important step in evaluating real returns. Below, we examine what “zero commission” really means, break down commonly overlooked hidden fees, and provide a framework for comparing costs—helping investors make more informed choices across platforms.

Background of zero-commission U.S. stocks: how the market evolved

To understand zero commission, you first need to know where the concept came from. Traditionally, buying and selling stocks requires paying trading commissions to a broker—either a fixed fee per trade or a percentage of the transaction amount. For frequent traders, these commissions can add up to a meaningful sum.

The rise of the zero-commission model

Starting in 2019, many major U.S. online brokers announced the removal of trading commissions for stocks and exchange-traded funds (ETFs), changing investors’ expectations around trading costs. After that, the model gradually expanded to Asia and Hong Kong, giving many local investors their first experience of lower-cost U.S. stock trading.

New opportunities for Hong Kong investors

For Hong Kong investors, the U.S. market offers opportunities to diversify a portfolio by gaining exposure to global companies across sectors such as technology, healthcare, and consumer. As low-cost trading platforms have become more widespread, the barriers to participation have fallen. If you’re considering getting started with U.S. stock investing, you can refer to this beginner’s guide to opening an account for U.S. stocks to learn the basic account-opening and trading rules.

Tip: The emergence of zero commission has reshaped the industry, but it doesn’t mean every platform has the same real costs. Comparing fees item by item helps you see the true cost clearly.

Zero commission doesn’t mean zero cost: hidden fees you need to know

This is the key to understanding true trading costs. “Zero commission” simply means the platform does not charge the traditional per-trade commission—but it does not mean trading has no costs at all. In reality, many other fees still apply, and some can be even harder to spot than commissions.

1. Platform fees and monthly fees

Some brokerages may not charge a commission per trade, but instead rely on “platform fees” charged monthly or per trade as a primary source of revenue. This fee model can be especially impactful for low-frequency traders: if you trade only once or twice a month, platform fees may make up a much larger share of your per-trade cost than traditional commissions.

Here’s a hypothetical example (for illustration only; not investment advice): if a platform charges a fixed platform fee per trade and the trade amount is small, the platform fee will represent a noticeably higher percentage of the transaction value. Therefore, when comparing platforms, you should consider the combined effect of commissions and platform fees.

2. FX conversion spread

Hong Kong investors typically hold funds in Hong Kong dollars (HKD), but need U.S. dollars (USD) to trade U.S. stocks. This currency conversion process is often an overlooked hidden cost.

When converting currency, banks or platforms usually add a spread on top of the market exchange rate as profit. Each deposit or FX conversion will incur this cost and reduce your usable funds. For investors who frequently deposit and withdraw, the FX spread can accumulate over time into a fairly significant expense.

3. U.S. regulatory fees

Under relevant U.S. regulations, each time you sell a stock, the platform will collect on your behalf the transaction fee levied by the U.S. Securities and Exchange Commission (SEC) under Section 31 of the Securities Exchange Act (SEC Section 31 transaction fee explanation), as well as the Trading Activity Fee charged by the Financial Industry Regulatory Authority (FINRA) (FINRA Trading Activity Fee). Although the amount per trade is relatively small, these are statutory fees, and platforms generally collect them according to the rates published by the regulators.

4. ADR fees

If you hold American Depositary Receipts (ADRs)—shares of certain non-U.S. companies listed on U.S. markets—the depositary bank may charge an annual ADR management fee to holders. This fee is usually deducted automatically from your account and appears on your monthly statement, but many investors may not notice it before opening an account.

5. Dividend withholding tax

This is one of the most commonly overlooked fees for Hong Kong investors, yet it can have a relatively large impact. Under U.S. tax law, dividends paid to non-U.S. tax residents are generally subject to a 30% statutory withholding tax (IRS NRA withholding explanation).

Here’s a hypothetical example (for illustration only; not investment advice): if a company declares a dividend of USD 1 per share, a Hong Kong investor would typically receive about USD 0.70, while the remaining 30% is automatically withheld by the platform and remitted to the U.S. Internal Revenue Service (IRS). Since Hong Kong and the U.S. have not signed a comprehensive income tax treaty, this 30% dividend tax generally cannot be reclaimed.

Note: For Hong Kong investors, capital gains from trading U.S. stocks (i.e., profit from the price difference between buying and selling) are not subject to capital gains tax in Hong Kong—this is a tax advantage. However, dividend taxation still applies, and you should pay particular attention when selecting dividend stocks or high-yield ETFs.

W-8BEN form: an essential document required when opening an account

When you open a U.S. stock trading account on an online brokerage platform, you will almost certainly need to complete a form called W-8BEN. This is a foreign status declaration required by the IRS, used to declare to the platform and U.S. tax authorities that you are a non-U.S. resident.

Why W-8BEN is important

Completing the W-8BEN does not exempt investors from the 30% dividend withholding tax, but it confirms your foreign investor status and helps prevent you from being treated as a U.S. tax resident—something that could trigger more complex tax filing requirements. The form is generally valid for three years and must be renewed upon expiry (IRS W-8BEN instructions).

Most modern online brokerages have digitized the W-8BEN, so you can typically confirm it online during the account-opening process without printing or mailing paper documents.

Points to note when completing W-8BEN

When filling it out, make sure the information matches your identity documents (such as your Hong Kong ID or passport). If the information does not match, it may affect your account status or tax processing. If you have any doubts, it’s recommended to consult a professional tax advisor before submitting.

How to choose a truly cost-effective U.S. stock platform

After understanding the various fees, how do you choose a platform that truly fits your needs? Below are several key dimensions to consider:

Calculate the true all-in cost

When choosing a platform, don’t focus only on the “zero commission” slogan—calculate the overall fee structure. It’s recommended to compare platforms across the following dimensions:

• Trading commission: Is it truly zero, or are there conditions and limitations?
• Platform fees: Charged monthly or per trade? How much is it?
• FX conversion spread: What exchange rate is used? Is there a cap?
• Deposit and withdrawal fees: Does it support Faster Payment System (FPS) or other fee-free deposit methods?
• Dividend collection fees: Some platforms charge extra fees for collecting dividends on your behalf

Regulatory credentials and fund protection

Beyond fees, a platform’s regulatory credentials are also worth paying attention to. Hong Kong investors may consider platforms licensed by the Securities and Futures Commission (SFC), where funds are subject to corresponding regulatory oversight. If you trade U.S. stocks through a U.S.-regulated broker, client assets are generally covered by the Securities Investor Protection Corporation (SIPC), up to USD 500,000 per customer (with a USD 250,000 limit for cash); SIPC protection does not cover losses caused by declines in securities prices (SIPC protection scope).

Trading tools and market information

Beyond costs, the quality of a platform’s trading tools and market information also affects the quality of investment decisions. Being able to track U.S. market quotes in real time and access in-depth financial analysis can help you make better-supported decisions at the right time. In addition, low-latency trade execution is particularly important for investors seeking precise entry timing.

Review the platform’s fee schedule before opening an account

Longbridge Securities provides U.S. stock trading services. In general, investors can review the selected platform’s publicly available fee schedule before opening an account to understand how commissions, platform fees, FX conversion, and other related charges are calculated, and then compare overall costs.

Fractional shares and entry threshold

One important feature of the U.S. stock market is that the minimum trading unit is one share, unlike the Hong Kong market, which trades in “board lots.” This means you can start investing by buying just one share, making the entry threshold flexible.

Some platforms also offer “fractional shares” trading, allowing investors to buy a small portion of a stock using a fixed amount. Here’s a hypothetical example (for illustration only; not investment advice): if a stock is priced at USD 500, an investor could buy about one-tenth of a share with USD 50. This gives smaller investors access to higher-priced stocks and helps diversify their portfolios.

Tip: Fractional-share trading is flexible, but some platforms apply different fee structures to fractional trades versus whole-share trades. Confirm the relevant fees before trading.

Key tax points for investing in U.S. stocks

For Hong Kong investors, the tax arrangement for U.S. stock investing is relatively favorable, but there are still several key points to note:

Tax treatment of capital gains

Hong Kong currently does not levy capital gains tax. Therefore, gains earned from trading U.S. stocks (price-difference profits) generally do not need to be reported or taxed in Hong Kong. This is a major advantage for Hong Kong investors compared with investors in many other regions.

Tax treatment of dividends

As noted above, dividends paid by U.S. companies to non-U.S. residents are generally subject to a 30% withholding rate, which applies to most Hong Kong investors. If your investment strategy focuses on regular dividend-paying stocks or high-yield ETFs, you should include this 30% dividend tax in your expected return calculations.

Reporting overseas income

If the total returns you earn from investing in U.S. stocks reach a certain scale, you may need to consult a Hong Kong tax advisor to understand whether there are any reporting requirements. Generally speaking, Hong Kong’s tax system is relatively friendly to individual investors, but the specifics vary from person to person.

FAQs

How do zero-commission U.S. stock platforms make money?

Although zero-commission platforms do not directly charge trading commissions, they typically generate revenue in the following ways: first, through “Payment for Order Flow” (PFOF), where exchanges or market makers pay brokers in exchange for routing client orders to them for execution (SEC PFOF explanation); second, through interest spreads earned on idle cash in client accounts; and third, through platform fees, advanced data service fees, or margin interest. Understanding a platform’s business model helps you assess whether its incentives align with your interests.

What taxes do Hong Kong investors pay when buying U.S. stocks?

Capital gains (price-difference profits) from trading U.S. stocks are not taxed in Hong Kong. However, dividends received are subject to a 30% U.S. dividend withholding tax, automatically deducted by the platform. Hong Kong and the U.S. have not yet signed a comprehensive tax treaty that would reduce dividend withholding rates, so this 30% rate usually cannot be reduced.

Is zero-commission trading suitable for all investors?

For frequent traders, zero commission can deliver more visible savings on commissions. But for long-term buy-and-hold investors, platform fees or other charges may matter more than commissions. When choosing a platform, investors can compare the total costs of different fee models based on their trading frequency and investment amount.

How can I confirm whether a platform has hidden fees?

Before opening an account, it’s recommended to read the platform’s publicly available fee disclosures carefully—pay particular attention to platform fees, FX rates, deposit/withdrawal fees, and ADR fees. If you’re unsure, you can contact the platform’s customer service directly to ask.

Conclusion

The arrival of the zero-commission era for U.S. stocks has indeed given more Hong Kong investors the opportunity to participate in global markets at lower costs. However, “zero commission” is only one dimension of trading costs. FX conversion spreads, platform fees, dividend withholding tax, and regulatory charges are the key factors that influence long-term investment returns.

When comparing different platforms, don’t rely solely on advertising slogans. Instead, compare fees item by item, and evaluate a platform’s regulatory credentials and tool quality, then decide which best fits your needs. Building investment knowledge is equally important: the deeper your understanding of market mechanics and cost structures, the more grounded your decisions will be.

Which tool or platform you choose depends on your investment objectives, risk tolerance, market views, and experience level. No matter which investment tool you choose, you must fully understand how it works, its risk characteristics, and trading rules, and establish a robust risk management plan. You can learn more through Longbridge Academy or download the Longbridge App.