One of the more notable constraints in the Trump Account structure is the investment restriction during the growth period. Until the year the beneficiary turns 18, account funds must be held in a single category of investment—and the parameters are specific. What Qualifies Eligible investments are mutual funds or exchange-traded funds (ETFs) that track a diversified U.S. equity index. The S&P 500 is the named reference point in the law, but other broad U.