Form 5329 has the penalty exceptions. You can see on page 4, that exception 3 matches your description, 2021 Instructions for Form 5329 - IRS. Your return will include the form and the exception so there is no penalty, simply the income. If the IRS ever decides to audit, then you would provide your proof.
**Say "Thanks" by clicking the thumb icon in a post
**Mark the post that answers your question by clicking on "Mark as Best Answer"