The specific identification method for cost basis lets you choose exactly which shares of a stock or fund are treated as sold, instead of letting your broker default to first-in, first-out. That choice controls your taxable gain or loss, but it only counts if you tell the broker which lot to sell at the time of the trade and get a written confirmation back. Miss either step and the IRS treats the sale as FIFO, no matter what you meant to do.
What the Method Actually Does for Your Taxes
Every time you buy the same security, you create a separate lot with its own purchase date and price. When you later sell, the gain or loss depends on which lot’s basis is used. Without an active choice, your broker applies FIFO, treating the oldest shares as sold first.1Internal Revenue Service. Stocks (Options, Splits, Traders) 1 If the stock has climbed, those oldest shares have the lowest basis and the largest built-in gain.
Specific identification lets you pick a different lot. Selling a high-cost lot shrinks the gain. Selling a lot you’ve held more than a year converts what would have been a short-term gain into a long-term one. For 2026, long-term capital gains are taxed at 0%, 15%, or 20% depending on income, while short-term gains hit ordinary rates as high as 37%. Choosing a lot held thirteen months instead of eleven can roughly halve the rate on the same dollar of profit.
The same lever works in reverse for tax-loss harvesting. If you want to generate a loss to offset gains elsewhere, you identify the lot with the highest basis relative to today’s price. That is the practical reason specific identification exists as a planning tool.
The Two-Part Rule That Makes an Identification Valid
Treasury Regulation 1.1012-1(c)(3) sets a two-part test when a broker holds your shares. You must tell the broker which particular shares to sell at the time of the sale, and the broker must send you a written confirmation of that selection within a reasonable time.2eCFR. 26 CFR 1.1012-1 Basis of Property Both parts are required. Skipping either one means the identification fails and FIFO applies by default.1Internal Revenue Service. Stocks (Options, Splits, Traders) 1
“At the time of the sale” is defined as no later than the settlement date, or the settlement time required under SEC rules.2eCFR. 26 CFR 1.1012-1 Basis of Property Since the standard settlement cycle moved to T+1 in May 2024, that window is one business day.3SEC. New T+1 Settlement Cycle – What Investors Need To Know The safe practice is to select lots before or at the moment you place the order. You cannot go back after settlement and pick different shares.
How to Tell Your Broker Which Shares to Sell
The information you provide has to be specific enough that there is no ambiguity about which lot you mean. That means the original purchase date, the price paid per share, and the number of shares from that lot.
Most brokerage platforms have a lot-selection tool built into the trade entry screen. When you enter a sell order, the platform shows your available lots with dates, quantities, and cost bases. You check the ones you want sold, and the system records the choice electronically. That satisfies the “at the time of the sale” requirement.
If the platform doesn’t offer lot selection online, send a written letter of instruction to the broker’s operations department before settlement. Include the security, the number of shares, and the specific lot identified by purchase date and price. Keep a dated copy.
Standing Instructions
You don’t have to pick lots trade by trade. The regulation treats a standing order or instruction for specific identification as an adequate identification made at the time of each sale.2eCFR. 26 CFR 1.1012-1 Basis of Property Most brokers let you set an account-wide default like highest-cost, first-out (HIFO) or last-in, first-out (LIFO), which then applies automatically to every sale unless you override it.
HIFO is the common choice for taxable accounts because it sells the most expensive lots first and automatically minimizes gains. The advantage of a standing instruction is that you never accidentally miss the settlement deadline and fall back to FIFO. If your broker only offers one specific-identification method, that method is treated as a standing order without further action from you. Look under your account’s “cost basis method” or “tax lot disposition” settings to see what’s active.
The Confirmation and the Paper Trail
After you submit a lot selection, the broker has to record it and give you written confirmation of which shares were sold.2eCFR. 26 CFR 1.1012-1 Basis of Property This is the second half of the regulatory test. Usually the confirmation appears as a notation on the trade confirmation issued within a day or two of the sale. Some brokers deliver a separate electronic message or post the detail in your transaction history. Either format works, but you have to keep it.
Store each confirmation with the original purchase records for that lot. The goal is a complete chain: the purchase confirmation showing basis, the lot-selection instruction, and the sale confirmation showing the broker honored your choice. If the IRS ever questions which shares you sold, that chain is the proof that the identification happened at the time of the trade rather than after.
The IRS requires you to keep property records until the statute of limitations runs on the tax year of the sale.4Internal Revenue Service. Topic No. 305, Recordkeeping Practically, keep the full chain for at least seven years after the sale to cover the longest limitations scenario.
Where Wash Sales Can Undo the Benefit
Specific identification is the standard tool for tax-loss harvesting, but the wash sale rule can wipe out the loss you were trying to capture. If you sell shares at a loss and buy substantially identical shares within 30 days before or after the sale, the loss is disallowed.5Office of the Law Revision Counsel. 26 USC 1091 – Loss From Wash Sales of Stock or Securities The disallowed amount gets added to the basis of the replacement shares, so the tax benefit shifts into the future rather than vanishing.
The trap for specific-identification users: you identify a losing lot and sell it, but you also purchased more of the same stock somewhere in the 61-day window around the sale. That purchase triggers the wash sale rule regardless of which lot you identified. When it applies, you report the sale on Form 8949 with adjustment code W and enter the disallowed loss as a positive number in column (g).6Internal Revenue Service. Instructions for Form 8949 Brokers usually flag wash sales on Form 1099-B, but their calculations don’t always catch transactions across different accounts or at different brokers, so verify the numbers.
Covered and Noncovered Shares
Whether your broker tracks basis for the IRS depends on when you bought the shares. Stocks acquired after 2010 and mutual fund shares acquired after 2011 are “covered securities,” and brokers must report basis on Form 1099-B.1Internal Revenue Service. Stocks (Options, Splits, Traders) 1 For those lots, the broker applies your chosen identification method and reports the result to the IRS.
Older shares are noncovered. The broker may still track basis internally, but nothing gets reported to the IRS, and you’re responsible for calculating and reporting the correct figure. When Box 1e on Form 1099-B is blank, you enter the basis directly on Form 8949.7Internal Revenue Service. Instructions for Form 8949 If you hold both covered and noncovered lots of the same stock, be careful about which ones you’re selecting, and make sure the broker’s records agree with yours.
The Mutual Fund Wrinkle
Mutual fund investors get an option stock investors don’t: the average basis method. You divide your total cost across all shares of the fund by the total shares owned, producing a single per-share basis.8Internal Revenue Service. Mutual Funds (Costs, Distributions, Etc.) Average basis simplifies recordkeeping in accounts with years of reinvested dividends creating dozens of small lots.
You can still use specific identification for mutual fund shares if you want the tax control. Which method wins depends on the spread between your lots. If you bought at roughly similar prices over time, average basis is fine. If some lots are much higher or lower in cost than others, specific identification gives you room to manage.
To affirmatively elect average basis on covered mutual fund shares, you notify the broker in writing (electronic counts). Many brokers set average basis as the default for mutual funds, and simply accepting that default is not the same as an election you made.2eCFR. 26 CFR 1.1012-1 Basis of Property The distinction matters if you later want to switch: an affirmative election has to be revoked in writing before the earlier of one year from the election date or the settlement of your first redemption. Once shares have been redeemed under an active average-basis election, the revocation window generally closes for those shares.
Reporting the Sale on Form 8949
Every sale where you used specific identification lands on Form 8949 and flows through to Schedule D. The form reconciles what your broker reported on Form 1099-B against the numbers you’re reporting.7Internal Revenue Service. Instructions for Form 8949 When the figures match, the entry is routine. When they don’t, you use adjustment codes to explain why.
The most common mismatch involves noncovered shares where the 1099-B basis field is blank; you fill in the correct basis in column (e). If the broker reported a basis that’s wrong, you use adjustment code B to correct it.6Internal Revenue Service. Instructions for Form 8949 The IRS matches 1099-B data against returns electronically, so unexplained differences tend to generate automated notices. The right adjustment code prevents that. If a notice does arrive, the purchase confirmation, the lot-selection record, and the sale confirmation for the lot in question usually resolve it.