Tax
Given the background of merger law against which the rules were set, historical tax overpayments and underpayments of companies composed of merged entities can be considered as a single amount, so long as no amounts are offset which were incurred by two companies which both had a distinct existence at the time of the payments.
(Reminder, as always, quick paraphrase of court on matter of public concern -- don't rely.)
WELLS FARGO & COMPANY v. US
Since 2011. An occasional commonplacing of the U.S. Circuit Courts of Appeal.
Neither an authoritative statement of the law nor legal advice. Quick work.