"Believing" is nice, but your question is not fully answerable without knowing whether the beneficiary is the father or someone else. In any event, Step 1 is to undo that intra-plan transfer and put the money (plus earnings, but probably not minus losses) in the son's account. There should be no tax-reporting associated with that erroneous transfer to the father's account. Let us know who the beneficiary is and we can help with Step 2.