Here's NiSource's exact wording in its Income Tax Footnote included as part of its 2017 Annual Report 10-K filed with the US SEC.
"Rates for NiSource’s regulated customers include provisions for the collection of U.S. federal income taxes. Accordingly, accounting effects related to changes in tax rates at NiSource that would normally be recognized as a component of income tax expense may instead be deferred as a regulatory asset or liability and reflected in future ratemaking. In December 2017, NiSource remeasured its deferred tax assets and liabilities to the new federal corporate income tax rate. The result of this remeasurement was a reduction in the net deferred tax liability of approximately $1.3 billion, including approximately $0.4 billion of regulatory "gross up" to account for over-collection of past taxes from customers. Offsetting the reduction in net deferred tax liabilities was an increase in regulatory liabilities of approximately $1.5 billion and an increase in income tax expense of $0.2 billion. These changes are discussed in further detail below."
I think just about everybody who overpays their taxes in the past will demand an immediate tax refund in cash. That is only fair.
