What form must a private foundation use to file an annual information return?

A private foundation is required to file Form 990-PF as its annual information return. This form is specifically designed for private foundations and includes comprehensive information about the foundation's finances, activities, and compliance with various tax regulations.

Form 990-PF not only provides details about the foundation's income, expenses, and assets, but it also allows the IRS to monitor the foundation's charitable activities, investment returns, and adherence to spending requirements. This is crucial because private foundations have unique tax obligations and distribution requirements, and Form 990-PF is structured to ensure transparency and compliance in these areas.

Other forms mentioned serve different purposes: Form 990-N is a simplified annual return for small tax-exempt organizations, Form 1023 is the application for recognition of exemption under section 501(c)(3), and Form 990-EZ is used by certain tax-exempt organizations not meeting the full requirements of Form 990. Thus, these forms do not fulfill the specific reporting requirements for private foundations, making Form 990-PF the appropriate choice.