A deferred income tax liability arises when book income exceeds taxable income. When this happens, a business recognizes a deferred income tax liability, which is based on the anticipated tax rate multiplied by the difference between these two types of income. It may be some time before this tax liability is actually paid, depending on the extent to which the taxpaying entity has deferred the liability. In the meantime, the liability appears on the organization's balance sheet.
The reason why a deferred liability arises at all is that the tax laws differ in some respects from the applicable accounting framework (such as GAAP or IFRS). For example, the tax laws might allow for the more rapid recognition of depreciation expense, while GAAP might allow for a more delayed recognition period. This means that an entity may recognize a higher income on its financial statements than on its tax return. An income tax liability should be recognized on the differential. As the business gradually recognizes depreciation on its financial statements, the liability is reduced in size, and eventually vanishes when all of the depreciation has been recognized.