Required Beginning Date (RBD) is the IRS-mandated deadline by which you must start taking required minimum distributions (RMDs) from certain tax-deferred retirement accounts, such as traditional 401(k)s and IRAs. It’s essentially the government’s way of ensuring that taxes are eventually paid on money that has grown tax-deferred. For most people, the RBD is April 1 of the year after you turn 73. After that, RMDs must be taken annually. Missing your RBD can lead to significant IRS penalties, so it’s important to know when it applies to you based on your birth year and account type.