26 CFR §1.483-2

1. (a)In general
   1. (1)Adequate stated interest. For purposes of section 483, a contract has unstated interest if the contract does not provide for adequate stated interest. A contract does not provide for adequate stated interest if the sum of the deferred payments exceeds—
      1. (i)The sum of the present values of the deferred payments and the present values of any stated interest payments due under the contract; or
      2. (ii)In the case of a cash method debt instrument (within the meaning of section 1274A(c)(2)) received in exchange for property in a potentially abusive situation (as defined in § 1.1274-3), the fair market value of the property reduced by the fair market value of any consideration other than the debt instrument, and reduced by the sum of all principal payments that are not deferred payments.
   2. (2)Amount of unstated interest. For purposes of section 483, unstated interest means an amount equal to the excess of the sum of the deferred payments over the amount described in paragraph (a)(1)(i) or (a)(1)(ii) of this section, whichever is applicable.
2. (b)Operational rules
   1. (1)In general. For purposes of paragraph (a) of this section, rules similar to those in § 1.1274-2 apply to determine whether a contract has adequate stated interest and the amount of unstated interest, if any, on the contract.
   2. (2)Present value. For purposes of paragraph (a) of this section, the present value of any deferred payment or interest payment is determined by discounting the payment from the date it becomes due to the date of the sale or exchange at the test rate of interest applicable to the contract in accordance with § 1.483-3.
3. (c)Examples. The following examples illustrate the rules of this section.
4. (d)Effective date. This section applies to sales and exchanges that occur on or after April 4, 1994. Taxpayers, however, may rely on this section for sales and exchanges that occur after December 21, 1992, and before April 4, 1994.