The math
The college account is a good idea and a smaller edge than you think.
A 529 is usually described as a no-brainer. On eighteen years of monthly saving the tax advantage over an ordinary brokerage account is 9.2%, and it runs both ways: if the money is not spent on education, you give back roughly the same amount.
What the account actually does
A 529 exempts investment growth from tax, provided the money is eventually spent on qualified education expenses. Contributions are made with money that has already been taxed federally, so unlike a 401(k) there is no deduction going in, though many states offer one against state income tax.
So the benefit is one exemption, not three. It shelters the growth. That is genuinely valuable and it is less valuable than it sounds, for a reason worth understanding.
Worked example
$300 a month for 18 years at 7%, with assumed rates of 15% long-term and 24% ordinary. $64,800 contributed in total
- 529, spent on qualified expenses
- $129,970
- Ordinary brokerage, after tax
- $118,997
- Advantage
- $10,973 (9.2%)
About eleven thousand dollars on sixty-five thousand contributed. Real money, and not the transformation the marketing implies.
Why the edge is modest
Because the thing it is being compared against is already tax-efficient.
A broad index fund held in a taxable account is taxed on its dividends each year, at the preferential rate, and not taxed at all on its appreciation until you sell. That is most of what a 529 offers, available in any brokerage account, with no restrictions on what the money is spent on.
The 529 adds the shelter on dividends and the exemption on the final gain. Over eighteen years at these assumptions that is worth 9.2%. Over forty years it would be worth far more, which is exactly why a retirement account is a bigger deal than a college account: it has twice as long to compound the shelter.
The 529's problem is not the tax treatment. It is that eighteen years is not very long, and children have a habit of arriving on a schedule.
Which makes starting early the entire mechanism
| Start at age | Years | Contributed | 529 | Taxable | Advantage |
|---|---|---|---|---|---|
| 0 | 18 | $64,800 | $129,970 | $118,997 | $10,973 |
| 5 | 13 | $46,800 | $76,443 | $71,624 | $4,819 |
| 10 | 8 | $28,800 | $38,684 | $37,130 | $1,554 |
| 14 | 4 | $14,400 | $16,659 | $16,313 | $346 |
Begin at birth and the shelter is worth $10,973. Begin at ten and it is worth $1,554. Begin at fourteen and it is worth $346, which is less than most people spend deciding which plan to open.
If your child is already in secondary school, the account structure barely matters. Save the money somewhere sensible and stop researching plans.
The part the brochures leave out
A 529 is a conditional benefit. The exemption applies only if the money goes to qualified education expenses. If it does not, the earnings are taxed as ordinary income and a 10% penalty applies on top.
If the money is not used for education
Same balance, withdrawn for something else
- 529, non-qualified withdrawal
- $107,812
- Ordinary brokerage, after tax
- $118,997
- Difference
- -9.4%
So the bet is close to symmetric: about 9% better if the money is used as intended, about 9% worse if it is not.
That symmetry is the honest frame, and it changes the decision from "obviously yes" to "yes if you are confident the money will be spent on education." Which for a newborn is a seventeen-year forecast about a person who does not exist yet.
It is not quite as binary as that sounds. Beneficiaries can generally be changed to another family member, unused amounts can in some circumstances be rolled into a retirement account for the beneficiary subject to limits, and qualified expenses now extend beyond university in several directions. Those options meaningfully soften the downside. They do not eliminate it.
What we would actually do
Check your state deduction first, because it may be the larger benefit. At a 5% state rate, deducting $64,800 of contributions is worth $3,240 of tax deferred, which is a meaningful fraction of the entire federal shelter. In states offering it, the deduction is often the main reason to use the account, and it usually requires using your own state's plan.
Fund it after retirement, not before. This is the one that matters most and the one people get backwards. Retirement accounts shelter for longer, often carry an employer match, and there is no scholarship or loan available for retirement. The order of operations applies here without exception.
Do not over-fund it. Given the symmetry above, the risk of putting too much in is real. Funding a plausible share of expected costs rather than the whole thing leaves room for scholarships, a cheaper school, or a child who does not go.
And invest it age-appropriately. Most plans offer an age-based option that shifts toward bonds as enrollment approaches, which exists because the order your returns arrive in matters enormously when the spending date is fixed. A 40% drawdown in a child's final year of secondary school is not recoverable the way it is in a retirement account.
What this leaves out
Contribution limits, income rules and state specifics. This essay prints none. They change annually and vary by state. Get them from the IRS and your own state's plan.
Financial aid treatment. Assets held in a 529 owned by a parent are generally assessed more favorably than assets held in the child's name, which can matter more than the tax treatment for families likely to qualify for aid.
And whether the cost itself is the right question. This essay prices an account. It says nothing about whether a particular degree is worth its price, which is a larger question and not one arithmetic settles.
Sources and further reading
- Publication 970, Tax Benefits for Education, Internal Revenue Service. The authoritative treatment of qualified expenses, the tax treatment of distributions, and the penalty on non-qualified withdrawals.
- Topic no. 313, Qualified tuition programs, Internal Revenue Service, for the definition of a 529 and how contributions and distributions are treated.