Definition
Cost basis is the amount assigned to an asset for measuring gain or loss, usually adjusted under applicable accounting and tax rules.
In market context
Basis may begin with purchase price and eligible transaction costs, then change because of distributions, splits, returns of capital, transfers, or other events. When units were acquired at different times, the permitted identification method can affect which basis is assigned to a disposal. A platform’s displayed average entry price may not equal tax basis, so original records and jurisdiction-specific rules remain important.
Source
Use the primary source for fuller regulatory or market context.
