The tax base of an asset or liability is the amount attributed to that asset or liability for tax purposes.
The tax base of an asset is the amount that will be deductible for tax purposes against any taxable economic benefits that will flow to an entity when it recovers the carrying amount of the asset. If those economic benefits will not be taxable, the tax base of the asset is equal to its carrying amount.
The tax base of a liability is its carrying amount, less any amount that will be deductible for tax purposes in respect of that liability in future periods. In the case of revenue which is received in advance, the tax base of the resulting liability is its carrying amount, less any amount of the revenue that will not be taxable in future periods.
