Tax Law, § 210(2)

The amount of subsidiary capital of the taxpayer (parent) is determined by computing the average value during the period covered by the report of all the assets of the taxpayer which constitute subsidiary capital, less any liabilities required to be deducted (see section 3-6.3 of this Subpart). Average value is determined in the manner which is described in section 3-3.6 of this Part. In no event may a subsidiary be valued at less than “zero.”