It depends on the type of mistake you made:
When filing an amended or corrected return:
Generally, to qualify for head of household, you must have a qualifying child or dependent. However, a custodial parent may be able to claim head of household filing status with a qualifying child even if he or she released a claim to exemption for the child.
To claim your child as your dependent, your child must meet either the qualifying child test or the qualifying relative test:
In addition to meeting the qualifying child or qualifying relative test, your child must also meet all of the other tests for claiming a dependent:
No, a dependency exemption for a child may only be claimed on one return in a tax year.
You may still qualify for head of household filing status even though you aren't claiming an exemption for your child, if you meet all of the following requirements:
You may be eligible to claim a dependency exemption for both your niece and her son on your return. In order to claim someone as your dependent, the person must meet certain tests as shown below.
The dependent must be:
Additionally, you must meet the dependent taxpayer test. If you can be claimed as a dependent by another person, you can't claim anyone else as a dependent.