Cost Basis Accounting (FIFO vs. SpecID)
The Formal Definition
The bookkeeping methodology used to determine which specific shares of a security are treated as sold when an investor holds lots purchased at different times and prices.
Realized Gain = Sale Proceeds - Cost Basis of Selected Lot (Specific Identification)
Cole Barrett's Reality Check
The Unvarnished Bottom Line"Never let your broker default you to First-In, First-Out (FIFO) without checking. If you sell 50 shares of Apple that you've held for years, FIFO sells your oldest, cheapest shares first—triggering the largest possible capital gains tax bill. Using Specific Identification lets you choose your highest-cost shares to minimize taxes."
Interactive Simulator: Test the Math
Real-World Example: Scenario Breakdown
Examining the real numbers for: Selling 100 shares of a stock after accumulating lots at $50, $80, and $110 (Current Price: $120)
| Execution Metric | Specific Identification (SpecID / Max Loss) | Default Broker FIFO (First-In, First-Out) |
|---|---|---|
| Fee / Rate | Selected $110 cost-basis lot to sell | Sold oldest $50 cost-basis lot |
| Spread / Buffer | Reported taxable capital gain: $10/share | Reported taxable capital gain: $70/share |
| Execution / Status | Total taxable gain: $1,000 | Total taxable gain: $7,000 |
| Total Cost / Result | Minimized immediate tax liability | Overpaid $1,200 in premature capital gains taxes |
How Brokers Weaponize This Term
Basic retail apps lock users into FIFO accounting to save on back-office accounting costs, forcing investors to realize larger taxable gains on partial portfolio sales.
Broker Evaluation Matrix
Cole Approves
Charles Schwab / Interactive Brokers: Tax Optimizer engines that let you select custom accounting methods (SpecID, LIFO, High-Cost) before settlement.
Read Audit →Cole Flags / Avoids
Basic Mobile Brokers: Locks taxable accounts into rigid FIFO reporting with no custom lot selection.
View Trap Details →Frequently Asked Questions
What is the best cost basis method for reducing immediate taxes?
The Highest-In, First-Out (HIFO) method generally minimizes immediate taxes by selling your most expensive shares first, reducing the realized capital gain.
Can you change your cost basis method after a trade settles?
In the US, you can update your lot selection with your broker as long as the change is submitted before the settlement date.