Hello.. beginner tax question on partial carryover of stock Example: A trader bought 10 shares of XYZ on December 1 2007. Then he sold 5 the week after. He then carried over 5 shares into 2008 and sold that in January 2008. What is the correct way to calculate the net profit for tax purposes? Could he split the 10 share purchase into two 5 share trades: use cancel one for 2007 and then use the second for 2008?