26 CFR §1.860C-1

1. (a)Pass-thru of income or loss. Any holder of a residual interest in a REMIC must take into account the holder's daily portion of the taxable income or net loss of the REMIC for each day during the taxable year on which the holder owned the residual interest.
2. (b)Adjustments to basis of residual interests
   1. (1)Increase in basis. A holder's basis in a residual interest is increased by—
      1. (i)The daily portions of taxable income taken into account by that holder under section 860C(a) with respect to that interest; and
      2. (ii)The amount of any contribution described in section 860G(d)(2) made by that holder.
   2. (2)Decrease in basis. A holder's basis in a residual interest is reduced (but not below zero) by—
      1. (i)First, the amount of any cash or the fair market value of any property distributed to that holder with respect to that interest; and
      2. (ii)Second, the daily portions of net loss of the REMIC taken into account under section 860C(a) by that holder with respect to that interest.
   3. (3)Adjustments made before disposition. If any person disposes of a residual interest, the adjustments to basis prescribed in paragraph (b)(1) and (2) of this section are deemed to occur immediately before the disposition.
3. (c)Counting conventions. For purposes of determining the daily portion of REMIC taxable income or net loss under section 860C(a)(2), any reasonable convention may be used. An example of a reasonable convention is “30 days per month/90 days per quarter/360 days per year.”
4. (d)For rules on the proper accounting for income from inducement fees, see § 1.446-6.