There will be no penalties if everything is complete by April 15th, including any repayment of tax. However if Dad receives extra refund for the dependent then he will have a repayment when the return is amended. Mom will file her return by mail if she want to put the dependent on her tax return. The IRS will not accept a second return with the same dependent social security number (SSN). Mom's return would get rejected if e-filed.
The amended form will be ready later in the year. By using the link, Tax Forms Availability, you can continue to check to see when it's ready. If you decide you do need to amend use the steps in the link below.
Be sure to amend your state return as well if applicable.
**Say "Thanks" by clicking the thumb icon in a post
**Mark the post that answers your question by clicking on "Mark as Best Answer"