Q. Why is the gain/loss on my PortfolioCenter performance reports different than the gain/loss on the PortfolioCenter tax reports? A. Comparing the gain/loss on performance reports to the gain/loss on realized gain/loss reports is comparing apples and oranges. The numbers almost never match.
On the Realized gain/loss report, the gain/loss is the gain/loss for tax purposes, i.e. the amount of gain or loss resulting from the sale or other disposal of a security. The tax gain/loss is computed using the purchase price and the value on the day of the sale.
On the Performance Reports, the gain/loss is the amount of gain during the time period of the report. This gain is computed from the market value of the security at the beginning of the reporting period, not from the purchase price.
The exception is when the security was purchased after the beginning of the reporting period. In that case, the purchase price is the same as the beginning market value and the apple and orange will be the same.