The amount (on an entity’s books) that is attributed to an asset for tax purposes. This amount will be deductible against “taxable” economic benefits that materialize from recovering the asset’s carrying amount.

For example, the tax base of a real estate “asset” is usually measured as a currency amount to which a tax rate is applied, that is the total monetary value of the real estate asset (in which case it is subject to a real property tax, i.e., a value-based tax).