The loss on 100 shares in the taxable account appears to result in the sale of those 100 shares being a wash sale because there was a purchase of 100 shares of the same stock in the Roth IRA less than 30 days earlier. Because the purchase was in a Roth account, the loss on the sale of 100 of the shares in the taxable account can never be realized because the loss increases the cost basis of the shares in the Roth IRA while per-share cost basis in a Roth IRA is meaningless. The purchase and sale of the other 900 shares would not be a wash sale.
