Why tax lot matters
Lot selection changes realized gain, holding period, remaining basis, and sometimes tax while leaving the number of shares sold unchanged.
How it is applied
Investors maintain acquisition records and choose specific identification, first-in-first-out, average cost, or other permitted methods before settlement deadlines. A tax lot records units acquired in one transaction or deemed acquisition, including date, quantity, adjusted cost basis, currency, and subsequent basis changes. Investors choose among permitted disposal methods such as specific identification, first-in first-out, or average cost, depending on jurisdiction, account, and security.
Portfolio example
Selling 100 shares from a $20 lot creates less gain than selling 100 shares from a $10 lot at the same market price. An investor buys 100 shares at 20 and another 100 at 35, then sells 100 at 40. Selecting the first lot realizes 2,000 gain; selecting the second realizes 500, before costs. The economic sale is identical, but current tax differs and remaining basis changes.
How to interpret it
Lowest-tax selection is not always best if it creates concentration or conflicts with portfolio objectives. Lot selection controls timing and character of realized gains and losses, not the security’s total pre-tax return. High-basis lots can reduce current gains, while preserving low-basis lots can defer tax. Holding period may affect applicable rates.
Limitations and common misconceptions
Permitted methods differ, broker defaults can apply, and wash-sale or equivalent rules may adjust replacement lots. Broker records can be incomplete after transfers, corporate actions, gifts, or old purchases. Rules restrict lot methods and require timely identification. Currency, return of capital, reinvested distributions, wash sales, and mergers alter basis. Minimizing today’s tax may increase future tax. Editorial content should explicitly distinguish a tax lot from an accounting inventory lot and avoid jurisdiction-free claims about permitted methods. Research tools should preserve acquisition date, basis adjustments, and disposal election. Link to cost basis, realized gain, tax-loss harvesting, and capital gains tax. For transferred accounts, investors should reconcile broker records against confirmations and prior tax statements before disposal. Missing basis may trigger unfavorable default reporting or require reconstruction. Corporate actions can create fractional lots and complex allocations. Portfolio software should preserve original source documents rather than overwrite history when a broker later updates an estimated basis.
Sources and further reading
- Publication 550: Investment Income and ExpensesU.S. Internal Revenue Service
- Dividends and Other Corporate DistributionsU.S. Internal Revenue Service