26 CFR §301.6511(f)-1 — (f)-1 Special rules for chapter 42 taxes.

1. (a)In general. Claims for credit or refund of an overpayment of any tax imposed by chapter 42 shall be filed by the taxpayer within 3 years from the time a return was filed by the private foundation or trust (as the case may be) with respect to such tax, or within 2 years from the time the tax was paid, whichever of such periods expire the later.
2. (b)Examples. This section may be illustrated by the following examples: