The value which is put on assets in a firm’s accounts. This may be the original purchase price, or a revised figure based on a periodic revaluation. It is contrasted with trying to value assets at their current market prices. Book value is often used when the assets are non-marketed, so that regular revaluation would be expensive and unreliable, or where the assets are marketed but their price is volatile, so that marking to market would produce very variable valuations. Balance sheets using book values may conceal either large hidden reserves or undeclared losses in a firm.