The OP was asking about a 401(k) not an IRA - the rules are different.
For a defined benefit plan such as a 401(k) you must take the first RMD by April 1 of the year following the later of the year you turn 70 ½ or the year you retire (if allowed by your plan). If you are a 5% owner, you must start RMDs by April 1 of the year following the year you turn 70½.
You need to check with the plan administrator. If you are still working and 86 then I would assume that the plan administrator would have already informed you if RMD's were required when you turned 70 1/2.
**Disclaimer: This post is for discussion purposes only and is NOT tax advice. The author takes no responsibility for the accuracy of any information in this post.**
