tax base並不是稅務的問題，
而是用於計算deferred tax assets / liabilities的
General Principles
This Statement deals with current taxes and deferred taxes. As its approach to deferred taxes is different from that contained in the superseded SSAP 12 "Accounting for deferred tax", some general principles relating to the treatment of deferred taxes in this Statement are set out below.
The future tax consequences of transactions and other events recognised in an enterprise's balance sheet give rise to deferred tax liabilities and assets, and are calculated in accordance with the following formulae:
Carrying amounts of assets or liabilities - Tax bases of assets or liabilities = Taxable or deductible temporary differences
Taxable or deductible temporary differences X Tax rates = Deferred tax liabilities or assets
Deferred tax assets also arise from unused tax losses that tax law allows to be carried forward, and are calculated in accordance with the following formula:
Unused tax losses X Tax rates = Deferred tax assets
The notion of temporary differences is central to understanding the requirements of this Statement. A taxable temporary difference gives rise to a deferred tax liability. A deductible temporary difference gives rise to a deferred tax asset. A taxable or deductible temporary difference arises when the carrying amount of an asset or a liability differs from its tax base. The meaning of "tax base" is of key importance to applying the requirements of this Statement. Tax base is defined in paragraph 5 of this Statement and is generally the amount that would be shown as an asset or a liability in a balance sheet prepared for tax purposes. Unlike the practice in some other countries, it is not customary in Hong Kong for enterprises to prepare tax-based balance sheets. However, the notion of a tax-based balance sheet is relevant to this Statement and may be used as a basis for working papers developed for the purpose of implementing this Statement.
This Statement generally requires an enterprise to recognise the tax consequences of transactions and other events consistently with the way that it recognises the transactions and other events themselves. Thus, for transactions and other events recognised in net profit or loss for the period, any related tax effects are also recognised in net profit or loss for the period. For transactions and other events that are recognised as direct credits to equity (direct debits to equity), any related tax effects are generally recognised as direct debits to equity (direct credits to equity).