A gain on an investment that has not yet been realized. That is, book profit occurs when the current price of a security is higher than the price the holder paid for it, but the holder still owns the security. As a result, there is the possibility that the book profit might be erased if the price goes back down. A book profit represents an increase in one's net worth, but it may or may not affect one's lifestyle. Under most circumstances, one is not taxed for book profit; the government waits until gains and losses are realized.
