The amount of the interest surcharge is determined by multiplying the “applicable percentage” of the deferred tax liability by the underpayment rate in effect at the end of the taxable year (with respect to tax deficiencies). The “applicable percentage” is determined by dividing the portion of the aggregate obligations for the year that exceeds $5,000,000 by the aggregate face amount of such obligations that are outstanding at the end of the taxable year. If an obligation remains outstanding in subsequent taxable years, interest must be paid using the same percentage rate as in the year of the sale.2 In addition, if the installment obligation is pledged as security for a loan, the net proceeds of the loan will be treated as a payment received on the installment obligation (up to the total contract price); however, no additional gain is recognized on subsequent payments of such amounts already treated as received. The date of such constructive payment will be (a) the date the proceeds are received or (b) the date the indebtedness is secured, whichever is later.3
1. IRC § 453A(b).
2. IRC § 453A(c).