401(k) custodians are usually pretty good about distributing required minimum distributions (RMDs) from the plans they oversee. This is especially important when a participant is rolling over his plan balance to an IRA. Why must plan custodians to be on their toes in situations like this? Because plan RMDs are not permitted to be rolled over to an IRA. Some people think they can roll their entire 401(k) to an IRA and simply take the plan RMD from the IRA later in the year. No deal. The plan RMD must be taken prior to any rollover. If the plan RMD is erroneously rolled over, it is now an excess contribution in the IRA, and that error must be corrected.