Final answer:
The correct answer is B. Corporation P is required to own at least 80% of Corporation S's voting stock to file a consolidated tax return. The 80% threshold ensures the parent corporation has sufficient voting control and economic interest in the subsidiary.
Step-by-step explanation:
Consolidated tax returns are filings that allow a parent company and its subsidiaries to file a single tax return, combining their incomes, deductions, and credits. In the context of corporations, stocks represent the ownership of the company, and voting stock specifically refers to shares that give the shareholder the right to vote on corporate matters.
In accordance with the Internal Revenue Service (IRS) regulations, for a parent corporation to include a subsidiary in its consolidated tax return, it must own at least 80% of the subsidiary's total combined voting power of all classes of stock entitled to vote and at least 80% of the total value of shares of all classes of stock. This control requirement is essential to ensure that the parent corporation has a dominant voting control and economic interest in the subsidiary, which justifies the combined tax reporting.