[Tax Optimization & Filing] How are US stock investments taxed? Practical guide to the 750 萬 tax‑exempt threshold for foreign income and 30% dividend withholding practice

30-second key takeaways (Key Takeaways)

Capital gains (price differences) and dividends that Taiwanese residents earn from investing in US stocks or overseas assets are considered "foreign income" and are subject to the minimum tax regime.
Individuals whose total annual basic income (including foreign income) does not reach NT$7,500,000 are fully exempt from the basic tax amount.
For non‑US tax residents investing in US stocks, the US government automatically withholds 30% dividend tax; filling out a W‑8BEN does not eliminate this withholding.
There are significant differences in tax documentation between omnibus/local and overseas brokers; with overseas brokers investors must consolidate statements and compute TWD cost basis themselves.
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1. Taiwan rules for reporting foreign income and the 750 萬 tax‑exempt threshold

Many Taiwanese investors who invest in US or HK stocks cross‑border worry most about complex tax issues. Under Taiwan’s "Minimum Tax System" (Basic Income Tax Act), residents’ non‑ROC‑source income (i.e., overseas income) is subject to rules if the annual total reaches NT$ 1,000,000，must be reported as part of the individual's basic taxable income.

However, it must be clarified that “reaching 1,000,000 requires declaration” does not necessarily mean “tax payable”. Under current regulation, an individual’s aggregate basic income amount below NT$ 7,500,000You receive the exemption and do not owe minimum tax. In other words, as long as your foreign capital gains and dividends are within NT$7,500,000, you effectively do not pay income tax in Taiwan.

overseas income brackets	Reporting obligation	Basic tax amount calculation
Annual total < 100 萬元	No reporting required	Not counted in basic taxable income
1,000,000 to 7,500,000	Must declare honestly	After deducting the 750 萬 exemption the result is 0; no tax payable.
Over 7.5 million 元	Must be reported and taxed	(basic income amount - 7,500,000) × 20%

2. US equities: 30% dividend withholding tax and W-8BEN form explained

In addition to Taiwan’s local minimum tax regime, investing in US stocks also faces US IRS withholding. As a Non‑Resident Alien, when you hold US stocks or US ETFs and receive cash dividends, brokers will automatically withhold ETF 30% Dividend withholding tax. This tax is deducted by the broker at dividend payment and does not require separate filing with the U.S. IRS.

Many investors hold the misconception that completing W-8BEN form(Foreign status certification) can reduce the 30% dividend rate to 0%. In practice, the W‑8BEN's main purpose is to prove you are 'not a US person' to avoid higher withholding under US domestic law and to receive standard treatment where there is no comprehensive tax treaty between the US and Taiwan. For Taiwan residents, dividend withholding on US stocks is fixed at 30% (investing in non‑US assets like Ireland‑domiciled UCITS ETFs can reduce withholding to 15% or even 0%). ETF

3. Tax and evidentiary differences: sub‑custody (複委託) vs overseas brokers

When choosing an access route, domestic brokers’ "entrusted overseas trading" (複委託) and opening a direct overseas broker account (e.g., Interactive Brokers, Firstrade, Charles Schwab) differ materially in tax treatment:

1. Domestic sub-brokerage / delegation (國內複委託):When domestic brokers handle overseas settlement, some brokers provide year‑end statements for foreign income, and the Ministry of Finance’s national tax e‑filing system may sometimes auto‑populate parts of the sub‑custody data, making documentation and tax filing relatively straightforward.

2. Offshore brokers:Investors must download the full‑year transaction statements (Statement) and the Realized Gain/Loss Report, and use the historical 台灣銀行 exchange rate on each trade date to convert USD to NTD for P&L calculations. If foreign income exceeds NT$7,500,000, investors must prepare all transaction vouchers for inspection by the 國稅局.

Frequently Asked Questions (FAQ)

Is the 7.5 million basic income tax‑exemption threshold for overseas income applied per individual or per tax filing unit?

The basic taxable income allowance (including foreign income, certain insurance benefits, etc.; currently adjusted to NT$7,500,000) is calculated per filing household. If spouses file jointly, the household’s total annual basic income allowance minus NT$7,500,000 is then taxed at 20% for the basic tax amount calculation.

Can the 30% US dividend withholding tax already deducted be credited against Taiwan income tax?

If your foreign‑sourced income is subject to Taiwan's basic tax amount (minimum tax regime), income tax paid overseas may be credited within limits against the difference between the basic tax amount and your regular income tax. However, if your basic tax amount does not reach the filing threshold, or your regular income tax already exceeds the basic tax amount, you cannot claim a refund or credit.

How long is the W-8BEN form valid? What happens if it expires?

The W-8BEN is valid from the date signed until December 31 of the third year following the year of signature。If the form expires and is not re‑signed, brokers may treat your account as a U.S. tax resident under IRS rules and apply up to 24% backup withholding on capital gains and withdrawals。Major brokers typically notify users by email several months before expiry to update the form online。

Advantages and target audience

A tax‑exempt threshold of 7,500,000 is very generous for most retail investors. With proper accounting, the tax burden on overseas investments is actually quite small.

Challenges and cautions

Tax documentation for overseas broker accounts requires complex manual calculations and currency conversions. If assets are large and exceed tax‑exemption thresholds, consult a professional accountant.

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