On the 2021 Form 990-W, the first paragraph in the instructions for line 10a is rewritten as follows. Subtract line 9 from line 8. Private foundations figure the estimated tax by multiplying their estimated net investment income by the 1.39% (0.0139) tax rate. Taxable private foundations and nonexempt charitable trusts treated as private foundations see Figuring and Paying Estimated Tax and Excise Tax Based on Investment Income (Section 4940(a), 4940(b), or 4948), in the Instructions for Form 990-PF, for help in figuring the estimated tax. Enter that amount on line 10a.