A. Money invested in 401(k) is subject to required minimum distributions (RMD). The general rule is that you must begin to take RMD by April in the year following when you turn age 70.5, and then take annual RMDs every subsequent year.
One exception is if you are still working for a company where you have 401(k). You may be able to delay taking RMDs on a 401(k) from a current employer until April after the year you retire. Any 401(k) from old jobs are not exempt, those RMDs must start at age 70.5.
If you also have traditional IRAs, there is no way to delay RMDs past age 70.5.