Specific Lot Identification
Specific lot identification is a cost basis accounting method permitted by the IRS in which an investor designates the exact purchase lot or lots being sold at the time of a transaction, enabling precise control over which embedded gains or losses are recognized and whether the holding period qualifies for long-term or short-term capital gains treatment.
The IRS requires that every capital asset sale be accompanied by a determination of cost basis — the original purchase price adjusted for commissions, reinvested dividends, return-of-capital distributions, and corporate actions. When multiple lots of the same security exist, the method used to assign basis to the shares being sold determines the taxable gain or loss for that transaction. Specific lot identification gives the investor maximum flexibility by allowing them to hand-select exactly which shares are considered sold.
To use specific lot identification, the investor must provide adequate identification of the shares being sold to their broker at or before the time of the sale. In practice, most modern U.S. brokerages support this electronically through their trading platforms, allowing investors to select individual lots from a dropdown menu when placing a sell order. The broker confirms the selection in the trade confirmation, which serves as the IRS documentation requirement.
The strategic value of specific lot identification is the ability to selectively realize losses while preserving long-term gains. Suppose an investor has bought 100 shares of the same stock in three separate purchases: the first 100 shares at $50 (held for 18 months), the second 100 shares at $80 (held for 8 months), and the third 100 shares at $90 (held for 3 months). If the stock trades at $75 and the investor sells 100 shares, specific lot identification allows them to sell the $80 or $90 lot to realize a short-term loss — which offsets ordinary income — rather than being forced by FIFO to sell the $50 lot and incur a long-term gain taxed at capital gains rates.
Specific lot identification is the method of choice for sophisticated tax-aware investors because it subsumes all other accounting methods. If an investor consistently applies HIFO logic — always choosing the highest-basis lot — specific lot identification produces the same result. If the investor wants to clear out small lots to simplify record-keeping while harvesting losses, specific lot identification enables that as well.
One important limitation is the wash sale rule: if the investor sells a lot at a loss and purchases a substantially identical security within 30 days before or after the sale, the loss is disallowed and deferred. Careful coordination of specific lot selection with wash sale rules is necessary to ensure that losses harvested through lot selection are not inadvertently negated by purchases in other accounts.