Today is National College Decision Day, the day when most colleges and universities require accepted students to submit a deposit if they plan to attend. These days, the down payment is just a tiny fraction of the total cost of tuition. To cover the difference, many parents are opting for 529 savings plans — college savings accounts that aren’t subject to any tax as long as the money’s used for tuition.

Marketplace Senior Producer of personal finance Paddy Hirsch explains how 529s work and how to decide if they are right for you.