a wash sale occurs when a security is sold at a loss and during the 30 days before or after the sale substantially identical securities are acquired. see below
example 1: if you sold all shares held on 12/27/2024 at a loss, any purchase on or before 1/27/2025 would result in a 2024 wash sale but only on the number of shares purchased due the period 12/27/2024 and 1/26/2025.
example 2: you sell only the shares acquired on 9/18 at a loss on 12/27/2024. you would have to wait until after 1/26/2025 to purchase more shares to avoid a wash sale.
example 3: you sell some shares at a loss on 12/27/2024. You buy substantially identical securities in your IRA account on 1/15/2025. A wash sale has been created.
the wash sales loss disallowed adds to the tax basis of the securities acquired that caused the wash sale (except in the case where the purchase is in a tax-exempt account like an IRA). In addition, the holding period of the original security tacks on the reacquired shares.
code section 1091
(a)Disallowance of loss deduction
In the case of any loss claimed to have been sustained from any sale or other disposition of shares of stock or securities where it appears that, within a period beginning 30 days before the date of such sale or disposition and ending 30 days after such date, the taxpayer has acquired (by purchase or by an exchange on which the entire amount of gain or loss was recognized by law), or has entered into a contract or option so to acquire, substantially identical stock or securities, then no deduction shall be allowed under section 165
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