Imputed underpayment.
(3) Imputed underpayment. Except as otherwise provided in this paragraph (a)(3), the term imputed underpayment means the amount determined in accordance with section 6225 of the Code, 301.62251, and, if applicable, 301.62252. In the case of an election under section 6226, the term imputed underpayment means the amount determined in accordance with 301.62263(e)(4). In the case of an administrative adjustment request, the term imputed underpayment means the amount determined in accordance with 301.62272 or 301.62273(c).