@chenhua00 - You still must report it as an excess using method #2 in the answer and add it back into your taxable wages since the deduction is not allowed.
If beyond the date to have it returned then it stays in the 401(k) plan and will be taxed again when finally withdrawn at retirement. That "double tax" is the penalty for not timely removing.
That is described in the IRS Pub "Excess not distributed".
For information see IRS Pub 525 page 10
<a rel="nofollow" target="_blank" href="
https://www.irs.gov/pub/irs-pdf/p525.pdf">https://www.irs.gov/pub/irs-pdf/p525.pdf</a>
**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.**