529s for Academy expenses is a complex area. Some have used them to pay USCGA expenses. However, cadets are not considered full time students by the IRS, they are active duty soldiers. As such, the academy does not issue 1099 forms for college expenses like civilian schools do. 1099s are needed to justify TAX FREE 529 draws on the tax return. But, because they are not college students, after their first year they do qualify for the savers credit which is a valuable tax credit.
The bottom line is with the IRS you can either be a active duty soldier or full time student, not both. There are different rules for each.
West Point has issued guidance that cadets are not to file as full time college students, providing at least one precedent on this complex matter.
@Don't Give Up the Ship gives an IRS accepted option to get your 529 funds out. As he says the 10% penalty is waived for academy kids. I would recommend an enhancement: as he describes if your cadet uses his pay to fund a Roth IRA (a very good idea), then that will make them eligible for the savers credit, and since they make about 13k a year as a cadet, the IRS credit is more than their tax. That extra credit can be used to cover the taxes due on 529 withdrawals. Careful planning is required but spreading the 529 non-qualified (taxable) withdrawals over 3 low earning academy years can lead to significant tax saving.
Great info from
@Don't Give Up the Ship .
A final FYI, USCGA will does several small loans as gear, laptops, etc. are issue, so it is kind of an ongoing process. Cadets only are required to buy books from the cadet store their first year. After that they can use Amazon or whatever saving significant funds.
Best to check with a tax accountant.