📈 Stock Basis Calculator
Track cost basis with dividends, splits & multiple purchases
📊 Purchase History
Lot 1
Total cost: $5,010.00
Lot 2
Total cost: $2,755.00
🔄 Adjustments
Dividend Reinvestment
Shares added: 3.448
Stock Split
Shares after split: 153.448
💰 Current Cost Basis
Total Shares
153.448
Total Cost Basis
$7,965
Avg Cost/Share
$51.91
Original Shares
153.448
Before split
💸 Calculate Capital Gain (Optional)
💡Tax Reporting Tips
- •Default method: IRS uses FIFO if you don't specify (oldest shares sold first)
- •Specific identification: Can choose which lots to sell for tax optimization (must tell broker before sale)
- •Record keeping: Keep all purchase confirmations, 1099-DIV forms, and split notices for audit protection
- •Broker accuracy: Verify broker's cost basis (they often miss pre-2011 purchases or reinvested dividends)
❓ Frequently Asked Questions
What is stock cost basis and why does it matter?
Cost basis is the original purchase price of a stock plus any adjustments (commissions, reinvested dividends, stock splits). It determines your capital gain/loss when selling: Capital Gain = Sale Price - Cost Basis. Example: Buy 100 shares at $50 ($5,000 basis) + $10 commission = $5,010 basis. Sell at $70 ($7,000) - $10 commission = $6,990. Capital gain = $6,990 - $5,010 = $1,980 taxable. Accurate basis calculation is crucial—understating basis means overpaying taxes, overstating basis triggers IRS penalties. Track every adjustment: reinvested dividends increase basis (you already paid tax on dividends, so don't pay again on sale), stock splits adjust per-share basis (2-for-1 split: $50/share becomes $25/share basis), return of capital reduces basis.
How do I calculate basis with dividend reinvestment?
Each reinvested dividend creates a new purchase lot with its own basis. Process: (1) Record dividend amount and reinvestment date, (2) Calculate shares purchased (dividend ÷ stock price on reinvestment date), (3) Add dividend amount to total cost basis. Example: Own 100 shares, $50 original basis/share = $5,000 total basis. Receive $200 dividend, reinvest at $55/share = 3.636 shares. New total: 103.636 shares, total basis $5,200 ($5,000 + $200). New average basis: $5,200 ÷ 103.636 = $50.18/share. Critical: Keep detailed records of each reinvestment—brokers often don't track pre-2011 basis correctly. Use specific identification method to minimize taxes: sell highest-basis shares first to reduce capital gains.