26 CFR § 1.507-7 - Value of assets.
(1) The first day on which action is taken by the organization which culminates in its ceasing to be a private foundation, or
(2) The date on which it ceases to be a private foundation.
(1) In the case of a termination under section 507(a)(1), the date referred to in paragraph (a)(1) of this section shall be the date on which the terminating foundation gives the notification described in section 507(a)(1).
(2) In the case of a termination under section 507(a)(2), the date referred to in paragraph (a)(1) of this section shall be the date of occurrence of the willful and flagrant act (or failure to act) or the first of the series of willful repeated acts (or failures to act) giving rise to liability for tax under chapter 42 and the imposition of tax under section 507(a)(2).
(d)Net assets. For purposes of section 507 and the regulations thereunder, the term net assets shall mean the gross assets of a private foundation reduced by all liabilities of the foundation, including appropriate estimated and contingent liabilities. Thus, a determination of net assets may reflect reductions for any liability or contingent liability for tax imposed upon the private foundation under chapter 42 with respect to acts or failures to act prior to termination, for any liability or contingent liability for failures to correct such acts or failures to act, or for any liability or estimated or contingent liability with respect to expenses associated with winding up the organization. If a private foundation's determination of net assets reflects any reduction for any estimated or contingent liability, such private foundation must establish, to the satisfaction of the Commissioner, the reasonableness of such reduction. If the amount of net assets reflects a reduction for any estimated or contingent liability, at the earlier of the final determination of the contingency or the termination of a reasonable time, any excess of the amount by which the gross assets was reduced over the amount of the liability shall be treated in the same manner as if such excess had been considered part of the net assets.