evidence: It’s known as the stepped-up basis rule, or, as President Joe Biden called it this month, the "trust fund loophole," and Biden’s American Families Plan aims to put an end to it for many people who inherit big estates. [...] The stepped-up basis provision, which has been used for decades to pass on wealth, was designed for that purpose. According to congressional records, the exemption was drafted in 1927 as a part of the Internal Revenue Act by House Ways and Means Committee Chairman William R. Green with help from Treasury Secretary Andrew Mellon, the son of one of the wealthiest families of the time. [...] Schoenberg said he favors throwing out the stepped-up basis rule, and supports taxing assets in full at inheritance. He concedes that getting there is a lot harder than it sounds.