A change in the reflected cost basis for your positions may occur if Tradesk does not receive the original cost basis information from your delivering brokerage firm for the transferred shares. If this occurs, the cost basis information displayed in your Tradesk account would then be based on the position's closing price on the day the position transferred into your Tradesk account.
The performance (P&L) you see in Tradesk is calculated based on this displayed cost basis price. This P&L is for visual display purposes only.
The true cost basis on the position will not be affected, as your original cost basis is unchanged on your tax documents.