Final answer:
Only partners' profits interests are considered for a majority interest taxable year, the principal partners test defines principal partners as those with 5% or more interest, and the least aggregate deferral test uses profits interests, not capital interests to determine tax year-end.
Step-by-step explanation:
Regarding the process for determining a partnership's tax year-end, the correct statement is that only the partners' profits interests are relevant when determining if a partnership has a majority interest taxable year. When applying the principal partners test, a principal partner is indeed someone who has a significant interest in the partnership, specifically defined as a partner with an interest of 5% or more in the profits or capital of the partnership, not 3% as the question suggests. Moreover, the least aggregate deferral test measures the amount of tax deferral a partnership could potentially achieve by choosing a particular tax year-end. This test uses the partners' profits interests, not their capital interests. Lastly, while it is a common default position to use a calendar year-end, a partnership is not absolutely required to use a calendar year-end solely because it has a corporate partner; it depends on the tax year-ends of the partners and the tests applied under the tax rules.