I have twin girls, both lived with me the entire year. After filing, 1 daughter says 7 months instead of 12 months under the Earned Income Credit. Do I need to amend?

[DanielV01]

No, it shouldn't be necessary.  Whether your daughter was with you for 7 or 12 months, she would still qualify for Earned Income Credit if you otherwise qualify.  If the IRS questions the residency, then you can respond to any letters proving she is your daughter (copy of birth certificate) and that she lived with you (medical or school records).  However, an amended return is not necessary to correct this particular piece of information on your return.