If you already filed your taxes and then discovered a 1099-R for money moved from an ESOP to a 401(k), you generally need to amend your return to include this form, even if the funds were rolled over immediately and no money was taken out. Here’s why:
- Reporting the 1099-R: Even though the rollover is non-taxable, you still need to report the 1099-R on your tax return to show the IRS that the distribution was rolled over. If you didn't include it in your original filing, you should amend your return to include this information.
You can use this IRS: Reporting Rollovers Tool to determine If you need to report the transfer or rollover of an IRA or retirement plan on my tax return?
To amend see steps at this link.