A Greek trireme. A Trireme is an ancient oar-driven warship powered by about 170 oars men. It was long and slender, had three tiers of oars and one sail. On the bow was a battering ram that was used to destroy enemy ships. The tip of the ram was made of bronze and could easily slice through the side of a wooden ship.
When you buy 1,000 shares of Ford at $14 and your broker charges you a $10 commission, your cost basis is $14,010 for those shares. That transaction is given a unique tax lot ID so you and the IRS can track those shares separately from other Ford stock you might buy later.
Cost basis is the original monetary amount paid for shares of a security. When you sell or exchange shares of mutual funds or other securities, you may have a capital gain or loss that must be reported to the IRS. For example, if you have a dividend reinvestment on 5/31 and an exchange redemption that results in a loss on 6/12 in the same tax year, some or all of the loss from your redemption may be disallowed as a wash sale. 2  The amount of the disallowed loss is added to the cost basis of the new shares.