Wash Sale Rules for Active US Stock Traders: 30-Day Disallowance Period and Substantially Identical Securities

The Internal Revenue Service’s 2025-2026 Priority Guidance Plan, released in late 2024, includes a long-awaited item: proposed regulations on the treatment of “substantially identical” securities under Section 1091 of the Internal Revenue Code. For the estimated 1.2 million US citizens residing in Hong Kong, many of whom maintain active trading accounts with US brokerages or Hong Kong-licensed platforms like Futu (Nasdaq: FUTU) and Tiger Brokers, this signals a potential tightening of the wash sale rules. The current guidance, last meaningfully updated in 2008 (Revenue Ruling 2008-5), leaves significant ambiguity around options, foreign securities, and cryptocurrency ETFs. A misinterpretation can lead to disallowed losses of USD 3,000 or more per tax year, triggering an IRS examination under the Compliance Assurance Process (CAP) or Correspondence Audit program. With the IRS’s Examination Division reporting a 14% increase in audits of high-income individuals for tax year 2023, the stakes for active traders have never been higher. This article dissects the 30-day disallowance period, the definition of substantially identical securities, and practical strategies for US citizens trading from Hong Kong.

The Mechanics of the 30-Day Disallowance Period

Section 1091(a) of the Internal Revenue Code imposes a wash sale rule: a loss from the sale or other disposition of stock or securities is disallowed if the taxpayer acquires, or enters into a contract or option to acquire, substantially identical stock or securities within a 61-day window—30 days before and 30 days after the sale date. The rule applies regardless of the taxpayer’s intent; a purely mechanical test governs.

The 61-Day Window and Its Application to Hong Kong-Based Traders

The 61-day period is fixed: it begins 30 days before the sale and ends 30 days after. For a US citizen residing in Hong Kong using a broker like Interactive Brokers (IBKR) or Charles Schwab, the sale date is determined by the trade date on the broker’s confirmation, not the settlement date. This distinction matters because Hong Kong’s T+2 settlement cycle for US stocks (per the Depository Trust & Clearing Corporation’s rules) can create confusion. If a trader sells shares of Apple Inc. (AAPL) on 1 March 2025 at a loss and then repurchases the same shares on 25 March 2025, the repurchase falls within the 30-day after period (ending 31 March 2025). The loss is disallowed and must be added to the cost basis of the new shares.

The disallowed loss is not permanently forfeited; it is deferred. The taxpayer’s holding period for the new shares includes the holding period of the old shares, and the adjusted basis is the original basis plus the disallowed loss. For a Hong Kong-based trader filing Form 1040 with Schedule D, this adjustment must be calculated manually if the broker does not provide wash sale adjustments. Interactive Brokers, for instance, applies wash sale adjustments to its tax reports for US-domiciled accounts but may not for accounts held through its Hong Kong entity (Interactive Brokers Hong Kong Ltd., regulated by the SFC under CE No. AVD796). Traders should verify their account classification.

The 30-Day Before Period and Short Sales

The rule also applies to acquisitions made before the sale. If a trader buys 100 shares of TSMC (TSM) on 10 February 2025 and sells 100 shares at a loss on 5 March 2025, the purchase on 10 February falls within the 30-day before period (starting 3 February 2025). The loss is disallowed. This provision catches traders who average down or add to a position before deciding to exit. For Hong Kong-based traders using margin accounts, a broker’s forced liquidation of a position to meet a margin call can trigger a wash sale if the trader repurchases the security within the 61-day window. The IRS has consistently held (see Revenue Ruling 71-316) that involuntary sales do not exempt the taxpayer from Section 1091.

Defining “Substantially Identical” Securities

The most contentious aspect of Section 1091 is the term “substantially identical.” The IRS has not issued a comprehensive regulation defining the term; instead, guidance is scattered across revenue rulings and case law. For active traders in Hong Kong, this creates particular risk when trading options, foreign securities, and exchange-traded funds (ETFs).

Options and Contracts to Acquire

Under Treasury Regulation § 1.1091-1(a), the term “stock or securities” includes options to acquire stock or securities. If a trader sells shares of Microsoft (MSFT) at a loss and within 30 days buys a call option on MSFT with a strike price near the current market price, the transaction is a wash sale. The IRS’s position, articulated in Revenue Ruling 85-87, is that a call option is substantially identical to the underlying stock if the option is deep in the money and the exercise is virtually certain. However, the ruling leaves ambiguity for at-the-money or out-of-the-money options. The proposed regulations expected in 2025-2026 may clarify this, but until then, traders should assume that any option on the same underlying security within 30 days of a loss sale will be scrutinized.

For Hong Kong-based traders using Hong Kong-listed options on the Stock Exchange of Hong Kong (SEHK), the analysis is more complex. Section 1091 applies to “stock or securities” as defined under the Internal Revenue Code. The IRS has not ruled on whether a Hong Kong-listed call option on a US stock (e.g., an option on Alibaba Group Holding Ltd. (9988.HK), which is a Hong Kong-listed secondary listing) is substantially identical to the US-listed Alibaba (BABA). The prudent position is to treat them as substantially identical if the economic exposure is equivalent, given the IRS’s functional approach in Revenue Ruling 2008-5.

Foreign Securities and ADRs

American Depositary Receipts (ADRs) and the underlying foreign shares are generally treated as substantially identical. In Revenue Ruling 2008-5, the IRS held that an ADR and the ordinary shares it represents are substantially identical if the ADR is convertible into the ordinary shares at a fixed ratio. For a Hong Kong-based trader holding both Tencent Holdings Ltd. (0700.HK) and the US-listed Tencent ADR (TCEHY), selling one at a loss and buying the other within 30 days creates a wash sale. This ruling is directly relevant to Hong Kong’s dual-listing market, where many Chinese companies trade both in Hong Kong and as US ADRs.

ETFs and Mutual Funds

The IRS has not ruled that two ETFs tracking the same index are substantially identical. In Revenue Ruling 58-210, the IRS held that shares of different mutual funds are not substantially identical even if they pursue similar investment objectives. However, this ruling predates the modern ETF era. The IRS’s position in Revenue Ruling 2008-5 suggests a facts-and-circumstances test: if the ETFs are managed by the same issuer, track the same index, and have identical holdings, they may be substantially identical. For a Hong Kong-based trader using Hong Kong-listed ETFs (e.g., the Tracker Fund of Hong Kong (2800.HK) vs. the CSOP Hang Seng Index ETF (3037.HK)), the risk of a wash sale challenge is low but not zero. The proposed regulations may address this.

Practical Strategies for Hong Kong-Based US Taxpayers

Active traders can mitigate wash sale risks through careful planning. The following strategies are grounded in the statutory framework and IRS guidance.

Timing Trades Around the 61-Day Window

The simplest strategy is to avoid repurchasing a substantially identical security within 30 days of a loss sale. For a trader using a Hong Kong-based account with a US broker, this requires tracking the 61-day window manually. Most brokers provide wash sale reports, but these are not always accurate for foreign accounts. The trader should maintain a separate log of all loss sales and the 30-day before and after dates.

Tax-Loss Harvesting with Non-Substantially Identical Securities

Tax-loss harvesting remains viable if the replacement security is not substantially identical. For a Hong Kong-based trader with a portfolio of US tech stocks, selling Microsoft at a loss and buying Apple within 30 days is generally safe, as the two stocks are not substantially identical. However, selling Microsoft at a loss and buying an ETF that holds Microsoft as a top holding is riskier. The IRS has not ruled on this, but the functional test in Revenue Ruling 2008-5 suggests that if the ETF’s sole purpose is to replicate Microsoft’s performance, it may be challenged.

Using Cash-Secured Puts and Covered Calls

A cash-secured put option that is exercised within the 61-day window can trigger a wash sale. If a trader sells a put on Nvidia (NVDA) and the put is exercised, the trader acquires the stock. If the trader had sold NVDA at a loss within the prior 30 days, the acquisition via the put exercise creates a wash sale. Conversely, writing a covered call on a position that is sold at a loss does not create a wash sale, because the call is a separate contract. The IRS has not addressed this directly, but the logic of Revenue Ruling 85-87 supports the distinction.

The Wash Sale and IRAs

A wash sale involving an IRA is particularly problematic. Under Revenue Ruling 2008-5, if a taxpayer sells stock at a loss and their IRA purchases substantially identical stock within 30 days, the loss is permanently disallowed—it cannot be added to the IRA’s basis. For a Hong Kong-based US citizen with a US-domiciled IRA (e.g., a Vanguard or Fidelity IRA), this is a critical trap. The IRA’s purchase of the same stock within the 61-day window triggers the rule, and the loss is lost forever. Traders should coordinate IRA and taxable account trading to avoid this.

The IRS Examination Cycle and Statute of Limitations

The IRS generally has three years from the filing date to assess additional tax for a wash sale error (IRC § 6501(a)). For a taxpayer who fails to report a wash sale properly, the statute of limitations remains open for three years. However, if the error is substantial (e.g., omitting more than 25% of gross income), the statute extends to six years (IRC § 6501(e)). For a Hong Kong-based trader filing Form 1040 with Schedule D, the IRS’s Automated Underreporter (AUR) program will compare the broker’s Form 1099-B to the taxpayer’s return. If the broker reports wash sale adjustments on Form 1099-B (Box 1g), the AUR will flag a mismatch if the taxpayer does not report the disallowed loss.

The IRS’s Large Business and International (LB&I) division has increased scrutiny of US citizens living abroad, particularly those with trading accounts exceeding USD 10 million. For a Hong Kong-based HNW trader, a wash sale error that leads to a disallowed loss of USD 50,000 could trigger an examination. The taxpayer should maintain detailed trade logs and broker confirmations to substantiate the wash sale adjustments.

Actionable Takeaways

• Maintain a separate trade log for all loss sales and track the 61-day window manually, as broker reports for Hong Kong-based accounts may not apply wash sale adjustments correctly.
• Treat ADRs and their underlying Hong Kong-listed shares as substantially identical under Revenue Ruling 2008-5; avoid buying one within 30 days of selling the other at a loss.
• Do not repurchase the same stock or a deep-in-the-money call option within 30 days of a loss sale, as the disallowed loss is deferred and can complicate future tax reporting.
• Coordinate IRA and taxable account trading to avoid permanent loss disallowance under Revenue Ruling 2008-5; a purchase in an IRA within the 61-day window forfeits the loss entirely.
• File Schedule D with accurate wash sale adjustments and retain broker confirmations for at least three years from the filing date to survive an IRS examination.

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This does not constitute tax advice. Consult a licensed CPA or tax advisor for your specific situation.