When President Trump signed the tax bill yesterday, there was an immediate effect on the reported earnings of every US company that reports using Generally Accepted Accounting Principles. The measurement of income tax expense under GAAP is based on the law as enacted and the President's signature is the final step in enactment. Deferred Tax LiabilitiesIf you write something off faster for tax purposes than for book purposes, you create a liability. Thanks to Section 179 you can treat that as an expense for income tax purposes, which under previous law might save you $35,000 on your corporate tax return. The significance of the President's signature is that the deferred tax liability is computed at "enacted rates".

Source: Forbes December 24, 2017 16:30 UTC