```html What is the Wash-Sale Rule and How Does It Affect Stock Day Traders? For active stock traders, particularly those engaged in day trading, understanding the intricacies of tax regulations is as crucial as mastering trading strategies. Among the most frequently misunderstood, yet potentially impactful, rules is the IRS's wash-sale rule. Designed to prevent taxpayers from claiming artificial losses for tax purposes, this rule can inadvertently catch even the savviest day traders off guard, altering their expected tax liabilities. This comprehensive guide will demystify the wash-sale rule, explain its core mechanics, and specifically detail its implications for stock day traders, offering practical advice to navigate its complexities. Understanding the Wash-Sale Rule The Core Definition The wash-sale rule, as defined by the IRS (Section 1091), states that if you sell stock or securities at a loss and then buy "substantially identical" stock or securities wit...