假售回购（英语：wash sale）是指投资人在目前亏损状况下售出证券（包含股票、债券、选择权），之后不久又买回相同或实质上相同的证券之行为。目的上，投资者是想将未实现资本损失转为已实现资本损失，以获得当年度税务抵免之优惠，并希望随后回购的证券在未来能增值产生资本利得，在未来年度才需报税。

目前一些国家针对这样的行为有税制上的防范。如美国，若在售出后30天内又回购相同证券，则实现亏损之交易会被调整为不具亏损，而将损失金额弥补至回购证券的交易成本基础（cost basis）上。整体来说，交易的亏损会被保留到日后又售出才真正实现，但在当年度该次交易则无法作为申报抵税用途。

A wash sale (not to be confused with a wash trade) is a sale of a security (stock, bonds, options) at a loss and repurchase of the same or substantially identical security shortly before or after.  The regulations around wash sales are to protect against an investor who holds an unrealized loss and wishes to make it claimable as a tax deduction within the current tax year. The security is then repurchased in the hope that it will recover its previous value, which would only become taxable in some future tax year. A wash sale can take place at any time during the year. In the UK, a similar practice which specifically takes place at the end of a calendar year is known as bed and breakfasting. In a bed-and-breakfasting transaction, a position is sold on the last trading day of the year (typically late in the trading session) to establish a tax loss. The same position is then repurchased early on the first session of the new trading year, to restore the position (albeit at a lower cost basis). The term, therefore, derives its name from the late sale and early morning repurchase.