Held for trading

Mark-to-market (MTM or M2M) or fair value accounting refers to accounting for the "fair value" of an asset or liability based on the current market price, or for similar assets and liabilities, or based on another objectively assessed "fair" value. Fair value accounting has been a part of Generally Accepted Accounting Principles (GAAP) in the United States since the early 1990s, and is now regarded as the "gold standard" in some circles, even though it is considered to be one of the reasons of the Enron scandal and the eventual bankruptcy of the company and the closure of the accounting firm Arthur Andersen.

Mark-to-market accounting can change values on the balance sheet as market conditions change. In contrast, historical cost accounting, based on the past transactions, is simpler, more stable, and easier to perform, but does not represent current market value. It summarizes past transactions instead. Mark-to-market accounting can become volatile if market prices fluctuate greatly or change unpredictably. Buyers and sellers may claim a number of specific instances when this is the case, including inability to value the future income and expenses both accurately and collectively, often due to unreliable information, or over-optimistic or over-pessimistic expectations of cash flow and earnings.

The practice of mark to market as an accounting practice first developed among traders on futures exchanges during the 20th century. It was not until the 1980s that the practice spread to major banks and corporations, and beginning during the 1990s, mark-to-market accounting began to result in scandals.

To understand the original practice, consider that a futures trader, when beginning an account (or "position"), deposits money, termed a "margin", with the exchange. This is intended to protect the exchange against loss. At the end of every trading day, the contract is marked to its present market value. If the trader is on the winning side of a deal, his contract has increased in value that day, and the exchange pays this profit into his account. On the other hand, if the market price of his contract has decreased, the exchange charges his account that holds the deposited margin. If the balance of this account becomes less than the deposit required to maintain the account, the trader must immediately pay additional margin into the account in order to maintain the account (a "margin call"). (The Chicago Mercantile Exchange, doing even more, marks positions to market twice a day, at 10:00 am and 2:00 pm).

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Wikipedia