When you sell part of a position in a taxable brokerage account, the broker must decide which purchase lots left the account. That choice—FIFO, LIFO, highest cost, lowest cost, average cost (common for mutual funds), or specific identification—changes your reported gain or loss on Form 1099-B and Form 8949. Set the method before you click sell when you care which dollars leave.
Where lots live: Taxable brokerage account basics. Basis corrections: 1099-B basis adjustment basics. Harvesting context: Tax-loss harvesting basics. Filing orientation: Filing taxes for beginners.
Common lot methods (orientation)
| Method | What it usually sells first | When people use it |
|---|---|---|
| FIFO (first in, first out) | Oldest lots | Broker default for many stocks/ETFs; can force long-held low-basis lots out |
| LIFO (last in, first out) | Newest lots | Sometimes useful if recent lots have higher basis (less gain) |
| Highest cost / tax-efficient | Lots with highest cost basis | Often used to minimize current gain or maximize current loss |
| Lowest cost | Lots with lowest cost basis | Can maximize current gain (sometimes intentional) |
| Specific identification | Exact lots you name in the trade ticket | Fine control for harvests and holding-period planning |
| Average cost | Blended basis across shares | Default for many mutual funds and some DRIP-heavy funds—see Average-cost basis for mutual funds |
Holding period (short-term vs long-term) still rides with the lot sold, not with “the ticker as a whole.” Capital-gains framing: Capital gains basics.
Specific ID vs hoping the default is fine
- Open the trade ticket’s cost-basis / lot relief panel at Fidelity, Charles Schwab, Vanguard Brokerage, E*TRADE, or your custodian before you submit.
- Prefer specific identification when you are harvesting a loss, avoiding a wash-sale adjacent lot, or protecting a long-term lot with huge embedded gain.
- Confirm the confirmation PDF lists the lots you intended; if it shows FIFO and you wanted specific ID, call the broker the same day—post-trade fixes are harder.
- For mutual funds on average cost, switching methods has IRS timing rules—do not assume you can flip mid-year without reading the fund/broker rules and current IRS Pub 550 cues.
DRIP purchases create many small lots; tracking them matters when you sell a slice: DRIP cost basis basics.
Worked example: FIFO vs specific ID on the same sale
Sam holds 300 shares of ETF ABC in a Schwab taxable account:
| Lot | Shares | Purchase date | Cost/share | Unrealized |
|---|---|---|---|---|
| A | 100 | Jan 2020 | $40 | Large long-term gain |
| B | 100 | Jun 2024 | $95 | Small short-term gain |
| C | 100 | Jan 2025 | $110 | Short-term loss of $10/share at a $100 sale |
Sam sells 100 shares at $100.
- Under FIFO, Schwab sells Lot A: roughly $6,000 long-term gain ($100 − $40) × 100.
- Under specific ID of Lot C, Sam books roughly $1,000 short-term loss—and keeps the low-basis Lot A intact for later planning (estate step-up, charitable gift, or a calmer year).
Same ticker, same proceeds, very different Form 8949. Sam screenshots the lot selection and keeps it with the 1099-B.
Habits that prevent surprise 1099-B lines
- Set a default lot method you understand; override per trade when harvesting.
- Export the open-lot report quarterly—especially after transfers (ACATS) and corporate actions.
- Coordinate household accounts before a harvest so you do not recreate a wash sale (Tax-loss harvesting basics).
- Do not invent basis on noncovered lots; reconstruct confirms first (1099-B basis adjustments).
- Remember IRAs and 401(k)s generally do not need lot ID for annual capital-gain reporting the way taxable accounts do.
Named custodians (Fidelity, Schwab, Vanguard, E*TRADE, Merrill Edge) publish lot-relief help articles; their UI labels change—trust the trade confirmation and year-end 1099-B.
Checklist
- Know your broker’s default lot method for stocks/ETFs vs mutual funds.
- Use specific ID when the tax dollars matter; verify the confirmation.
- Match holding periods to the lots you actually sold.
- Keep lot exports with your tax folder for Form 8949.
- Read mutual-fund average-cost rules before you switch methods.
- File with Filing taxes for beginners habits: reconcile 1099-B to your lot list.
After a split, confirm post-split lot counts before you specific-ID a sale: Stock split cost basis basics.
Educational only. Not tax, investment, or accounting advice. Lot-identification and basis rules are technical; confirm with IRS publications, your custodian’s cost-basis tools, and a qualified tax professional.