For the earned income credit can I count all dependents or is it just qualifying children?

Only a "Qualifying Child" dependent qualifies your for the Earned Income Credit and Child Tax Credit and Head of Household filing status.

 

Although a domestic partner's child might qualify as your "other dependent", for the $500 other dependent credit, they cannot qualify you for EIC,  CTC,  or HoH, because they are not related. 

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There are two types of dependents, "Qualifying Children"(QC) and standard/other ("Qualifying Relative" in IRS parlance even though they don't have to actually be related). There is no income limit for a QC but there is an age limit, student status, a relationship test and residence test. Only a QC qualifies a taxpayer for the Earned Income Credit and the Child Tax Credit. They are interrelated but the rules are different for each.

The support test is different for each type. The support test, for a QC, is only that the child didn't provide more than half his own support. The support test for a Qualifying Relative is that the taxpayer provided more than half the relative's support.

.A child closely related to a taxpayer can be a “Qualifying Child (QC)” dependent, regardless of the child's income, if:

1. He is under age 19, or under 24 if a full time student for at least 5 months of the year, or  is totally & permanently disabled
2. He did not provide more than 1/2 his own support
3. He lived with the relative (including temporary absences) for more than half the year
4. He is younger than the relative (not applicable for a disabled child)
5. If the child meets the rules to be a qualifying child of more than one person, you must be the person entitled to claim the child as a qualifying child (this essentially means that you have the parent’s permission to claim the child, if the child also lived with the parent more than half the year)
6. If the parents of a child can claim the child as a qualifying child but no parent so claims the child, no one else can claim the child as a qualifying child unless that person's adjusted gross income (AGI) is higher than the highest AGI of any of the child's parents who can claim the child.

See full dependent rules at: https://turbotax.intuit.com/tax-tools/tax-tips/Family/Rules-for-Claiming-a-Dependent-on-Your-Tax-Return/INF12139.html

 

A person can still be a Qualifying relative (other) dependent, if not a Qualifying Child, if he meets the 6 tests for claiming a dependent:

1. Closely Related OR live with the taxpayer ALL year
2. His/her gross taxable income for the year must be less than $4300 (2020).
3. The taxpayer must have provided more than 1/2 his support

In either case:

4. He must be a US citizen or resident of the US, Canada or Mexico
5. He must not file a joint return with his spouse or be claiming a dependent of his own
6. He must not be the qualifying child of another taxpayer

He must have a US social security number or tax identification number (TIN)

In addition to the above requirements, to claim your domestic partner's children, they must meet all of the above requirements and:
--- your partner must not be required to file a return,
--- he/she does not file a return claiming the children

Only the kids if they qualify ... 

• What is a qualifying child for the Earned Income Credit (EIC)?

Must be your qualifying child.

 

To be your qualifying child, a child must be your:
• Son, daughter, stepchild, foster child, or a descendant
of any of them (for example, your grandchild); or

• Brother, sister, half brother, half sister, stepbrother,
stepsister, or a descendant of any of them (for exam-
ple, your niece or nephew).

 

See IRS pub 596

https://www.irs.gov/pub/irs-pdf/p596.pdf

Only your children for the earned income tax credit.