529 plan vs. a taxable brokerage account

Why the gap exists

Both accounts hold the same kind of investments and can target the same return before taxes. The difference is entirely in what the IRS takes along the way. A taxable account owes tax each year on dividends and any realized capital gains, which quietly shaves a percentage point or more off the compounding return every single year. A 529 plan defers all of that — nothing is owed as the account grows, and nothing is owed on withdrawal either, as long as the money pays for qualified tuition, fees, room, board, and required books or equipment.

Over a single year the tax drag looks small. Compounded over a decade or more, it is the entire difference shown above — the 529's edge isn't a better underlying investment, it's the same investment without a yearly tax bill eating into the base it compounds from.

When the taxable account is the better tool

• You aren't certain the money will be spent on qualified education costs — a taxable account has zero restrictions or penalties on how it's used.
• You've already maxed out 529 contributions that qualify for a state income-tax deduction (some states cap the deductible amount per year).
• You want the flexibility to shift the money to a completely different goal without a 10% penalty on the earnings.