One result of the 1976 effort unifying the federal estate and gift tax was that "adjusted taxable gifts" after 1976 are taken into account in determining cumulative transfers at death. This is the mechanism by which use of any part or all of the unified estate and gift tax credit during life is taken into account at death.
A major question that has been repeatedly litigated in recent years is whether IRS after death can revalue lifetime gifts falling within the category of adjusted taxable gifts. The predominant view emerging from the cases is that IRS may indeed revalue such gifts even though the period of time for challenging gift tax liability has expired.
Harl, Neil E.
"Revaluing Prior Gifts at Death,"
Agricultural Law Digest: Vol. 5
, Article 1.
Available at: https://lib.dr.iastate.edu/aglawdigest/vol5/iss4/1