Specific Share Identification

Specific share identification is the method of designating which specific shares, out of a position accumulated through separate purchases at different prices and dates, are being sold in a given transaction. Treasury Regulation 1.1012-1(c) is the governing rule, though the regulation does not use the phrase "specific share identification" as its own defined term. It instead requires an "adequate identification" of the shares sold, and specific share identification, sometimes called specific lot identification, is the common name for satisfying that requirement.

The reason the method exists is that the same stock bought on different occasions can carry very different bases and very different holding periods, so which shares a sale draws from can materially change both the size of the gain and whether it is taxed as short-term or long-term.

The regulation's requirement is precise about timing, and the timing is the part most often missed. Treasury Regulation 1.1012-1(c)(3) provides that for shares held with a broker or other agent, an identification is adequate where, at the time of the sale or transfer, the taxpayer specifies to that broker or agent the particular shares to be sold, and, within a reasonable time afterward, the broker or agent confirms that specification in writing. Both halves matter: the instruction has to be given at the moment of the trade, and it has to be followed by written confirmation. A taxpayer who simply decides later, when preparing a tax return, which shares they meant to sell has not made an adequate identification, because the regulation requires the choice to be made at the transaction itself, not reconstructed afterward.

What the identification actually controls is the gain's size and its character, and those two effects can pull in different directions. Identifying the highest-basis lot available generally minimizes the taxable gain on the sale, or maximizes a deductible loss, since a higher basis means a smaller spread between basis and sale proceeds. Identifying the longest-held lot can instead be used to secure long-term treatment on shares that would otherwise be short-term, even where that lot has a lower basis and produces a larger gain. Which of these matters more depends on the investor's situation: someone harvesting a loss wants the highest-basis lot regardless of holding period, while someone trying to avoid short-term rates on an otherwise appreciated position may accept a somewhat larger gain in exchange for long-term treatment. Specific identification is the only one of the basis methods that gives the investor this kind of direct control over the outcome, lot by lot, at the time of each sale.

Nothing about specific identification changes how the underlying basis of each lot was established or how it is adjusted over time. The regulation governs which lot a sale is charged against; it does not change the basis of any particular lot, which is set at acquisition and then adjusted for events such as reinvested distributions, exactly as covered on the page for cost basis. Specific identification is a tool for choosing among already-established lots, not a way to change what any one lot's basis is.

Miss the moment, and the default rule takes over automatically. Treasury Regulation 1.1012-1(c)(1)(i) provides that where a taxpayer sells shares of stock and does not adequately identify which shares were sold, the shares are charged against the earliest lot purchased or acquired, which is the first-in, first-out default. There is no way to retroactively claim a specific identification after the sale has already settled without one; the earliest-lot default has already applied by then. This is why the identification is described as a choice made at, or before, the moment of sale rather than a preference recorded at any later point.

Mutual fund shares eligible for the average basis method are a partial exception worth flagging, even though this page is about the general stock rule. A shareholder who has elected the average basis method for eligible mutual fund or dividend reinvestment plan shares is generally bound by that election going forward for those shares, which limits the ability to switch to specific identification for that position afterward. The average basis method itself, including which shares are eligible for it, is covered on its own page.

At or before the time of a sale, the shareholder tells the broker which specific lot of shares to sell. The broker executes the sale against that lot and sends written confirmation of the identification within a reasonable time afterward, and the gain or loss is then computed using that lot's basis and holding period rather than any other lot in the account.

A hypothetical example. Yusuf owns 300 shares of the same stock, bought in three separate purchases: 100 shares in 2019 at $20 each (basis $2,000), 100 shares in 2022 at $45 each (basis $4,500), and 100 shares in 2025 at $60 each (basis $6,000). The stock now trades at $70. He wants to sell 100 shares and needs the cash, but wants to minimize the taxable gain.

Without an identification, the sale defaults to the 2019 lot under first-in, first-out, producing a gain of $5,000 (100 × $70 − $2,000). Instead, before placing the order, Yusuf specifically identifies the 2025 lot to his broker. The sale is charged against that lot's $6,000 basis, producing a gain of $1,000 (100 × $70 − $6,000), which is $4,000 smaller than the default would have produced ($5,000 − $1,000), though it is a short-term gain rather than the long-term gain the 2019 or 2022 lots would have produced.

Pros

• Gives direct, lot-by-lot control over the size and character of a gain or loss, which no other basis method offers.
• Makes precise tax-loss harvesting possible, since a specific high-basis or underwater lot can be targeted for sale without disturbing the rest of the position.
• Can be used to secure long-term treatment on part of a position while leaving other lots untouched.
• Works alongside ordinary broker recordkeeping, since brokers report basis by lot for covered securities and can act on an identification instruction directly.

Cons

• The identification has to be made at the time of the sale, so an investor who forgets, or decides later which lot they meant, loses the choice entirely.
• Requires actively tracking multiple lots and their bases, which is more bookkeeping than accepting the automatic default.
• Not available, or meaningfully limited, once average basis has been elected for eligible mutual fund or dividend reinvestment plan shares.
• Choosing the lot that minimizes the current gain can sometimes mean accepting short-term treatment on the sale, trading a smaller gain now for a higher tax rate on that gain.