Is it too late to start a 529 if my child is already a teenager?

No — it's never too late, though your strategy should shift. Starting late means less time for compounding, so focus on contributing as much as you comfortably can rather than relying on growth, and choose a more conservative investment mix (or a target-enrollment portfolio near its end date) to avoid a market drop wiping out savings right before tuition. Even a 529 opened in your child's junior year of high school can capture your state tax deduction on contributions and provide tax-free growth on whatever you put in. You can also contribute to a 529 and withdraw shortly after for that year's expenses, effectively using it as a tax-deduction pass-through in states that allow it. Model a realistic catch-up plan at wealthserene.com/goals/plan-for-college.