Excise Tax (IRC Section 4940)
Effective for tax years starting after December 20, 2019, a private foundation is subject to an annual excise tax equivalent to 1.39% of its net investment income.
The tax is calculated and paid annually along with the foundation's filing of IRS Form 990-PF. If the excise tax is expected to be greater than $500, then the foundation will need to make estimated quarterly tax payments. Calculations for the estimated tax payments can be made using IRS Form 990-W and paid through the Electronic Federal Tax Payment System (EFTPS), www.eftps.gov.
Note: Some private operating foundations are not subject to this tax. Refer to the IRS definition of an exempt operating foundation for details.