What is Mark To Model?

Legal Definition
Mark-to-Model refers to the practice of pricing a position or portfolio at prices determined by financial models, in contrast to allowing the market to determine the price. Often the use of models is necessary where a market for the financial product is not available, such as with complex financial instruments. One shortcoming of Mark-to-Model is that it gives an artificial illusion of liquidity, and the actual price of the product depends on the accuracy of the financial models used to estimate the price. On the other hand it is argued that Asset managers and Custodians have a real problem valuing illiquid assets in their portfolios even though many of these assets are perfectly sound and the asset manager has no intention of selling them. Assets should be valued at mark to market prices as required by the Basel rules. However mark to market prices should not be used in isolation, but rather compared to model prices to test their validity. Models should be improved to take into account the greater amount of market data available. New methods and new data are available to help improve models and these should be used. In the end all prices start off from a model.
-- Wikipedia
Legal Definition
Security's cost projection using prior projection figures information. An auditable method. Investors' gained profit margin potentially false if using a stock's higher-yield investment price.
Legal Definition
Using mathematical model rather than the market price to demean value.