26 U.S.C. § 6206: Special rules applicable to excessive claims under certain sections

Any portion of a refund made under section 6416(a)(4) and any portion of a payment made under section 6420, 6421, 6427, or 6435 which constitutes an excessive amount (as defined in section 6675(b)), and any civil penalty provided by section 6675, may be assessed and collected as if it were a tax imposed by section 4081 (with respect to refunds under section 6416(a)(4) and payments under sections 6420, 6421, and 6435), or 4041 or 4081 (with respect to payments under section 6427) and as if the person who made the claim were liable for such tax. The period for assessing any such portion, and for assessing any such penalty, shall be 3 years from the last day prescribed for the filing of the claim under section 6416(a)(4), 6420, 6421, 6427, or 6435, as the case may be.