If your teenager earned money this year, they can fund a Roth IRA. That's the only real requirement: earned income, reported. Mowing lawns and babysitting count if you're keeping records of it, and a W-2 makes it simpler.
The contribution is capped at the lesser of what they earned or the annual IRA limit. So a kid who made $3,000 at a summer job can put in $3,000, not a dollar more.
The part parents miss is that the money doesn't have to be the same money. Your kid can spend the paycheck like a teenager and you can fund the Roth for them up to what they earned. The IRS cares that the earned income existed, not which dollars made the trip. That's usually the difference between this happening and not happening.
It's a custodial Roth until they hit the age of majority in your state, which means you manage it and it becomes theirs at 18 or 21. Contributions can come back out at any age, tax-free and penalty-free, because that money was already taxed. Earnings are the part with rules attached. So the account is not a locked box, which matters to a 17-year-old deciding whether to bother.
The reason to do it at 16 instead of 26 is the runway. A dollar in this account has fifty years to work before anyone touches it for retirement, and it comes out untaxed at the end. There is no other window in a person's life that long.
Two practical notes. Keep records if the income is informal, since a log of dates, hours, and who paid is what makes it real if anyone ever asks. And you've got until the April tax deadline to fund the prior year, so a summer job in 2026 can still be funded the following spring once you know the final number. I'm a licensed insurance broker rather than a CPA, so confirm the documentation with your tax preparer before you file.