(a) General rule In the case of a citizen or resident of the United States, there shall be allowed as a credit against the tax imposed by section
2501 for each calendar year an amount equal to
(1) the applicable credit amount in effect under section
2010 (c) for such calendar year (determined as if the applicable exclusion amount were $1,000,000), reduced by
(2) the sum of the amounts allowable as a credit to the individual under this section for all preceding calendar periods.
(b) Adjustment to credit for certain gifts made before 1977 The amount allowable under subsection (a) shall be reduced by an amount equal to 20 percent of the aggregate amount allowed as a specific exemption under section
2521 (as in effect before its repeal by the Tax Reform Act of 1976) with respect to gifts made by the individual after September 8, 1976.
