Deferred tax : tax base confusion

I was going thru this chapter and had clarity till i reached the section of handling deferred tax for lease. Tax base definition : Asset : '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' Liability: The tax base of a liability is its carrying amount, less any amount that will be deductible for tax purposes in future periods. in the examples given for temporary difference calculations. Where no temporary difference arises An entity enters into a lease agreement and the present value of the payments to be made is $4 million. It records the following accounting entry: Dr Right-of-use asset $4m Cr Lease liability $4m The right-of-use asset and lease liability both have a carrying amount of $4 million. If the tax jurisdiction grants tax relief in respect of the leased asset then: ? the right-of use asset has a tax base of $4 million (the future allowable tax deduction) ? the lease liability has a tax base of $4 million (carrying amount less any amount that will be deductible for tax purposes in future periods i.e. $4m – nil). No temporary differences arise on initial recognition of the transaction and so no deferred tax is accounted for. Deferred tax will be recognised subsequently if temporary differences arise. There is difference in treatment when relief is given on leased asset or lease liability. My Question : When relief is given on leased asset why is the tax base 4m should it not be nil ? because in the initial example early in the chapter there was relief (capital allowance full amount) on asset and the tax base was taken as nil. why the liability has a nil tax base as its not even qualified for relief. really confused.