Per IRS Publication 503 Child and Dependent Care Expenses, on page 3:
Who is a Qualifying Person?
Your child and dependent care expenses must be for the care of one or more qualifying persons.
A qualifying person is:
Dependent defined. A dependent is a person, other than you or your spouse, for whom you could claim an exemption. To be your dependent, a person must be your qualifying child (or your qualifying relative). However, the deductions for personal and dependency exemptions for tax years 2018 through 2025 are suspended, and therefore, the amount of the deduction is zero. But in determining whether you may claim a person as a qualifying relative for 2020, the person's gross income must be less than $4,300, not zero.
Qualifying child. To be your qualifying child, a child must live with you for more than half the year and meet other requirements.
More information. For more information about who is a dependent or a qualifying child, see Pub. 501.
Physically or mentally not able to care for oneself. Persons who can't dress, clean, or feed themselves because of physical or mental problems are considered not able to care for themselves. Also, persons who must have constant attention to prevent them from injuring themselves or others are considered not able to care for themselves.
Person qualifying for part of year. You determine a person's qualifying status each day. For example, if the person for whom you pay child and dependent care expenses no longer qualifies on September 16, count only those expenses through September 15. Also see Yearly limit under Dollar Limit, later.
Birth or death of otherwise qualifying person. In determining whether a person is a qualifying person, a person who was born or died in 2020 is treated as having lived with you for more than half of 2020 if your home was the person's home more than half the time he or she was alive in 2020.
Taxpayer identification number. You must include on your return the name and taxpayer identification number (generally, the social security number) of the qualifying person(s). If the correct information isn't shown, the credit may be reduced or disallowed.
Individual taxpayer identification number (ITIN) for aliens. If your qualifying person is a nonresident or resident alien who doesn't have and can't get a social security number (SSN), use that person's ITIN. The ITIN is entered wherever an SSN is requested on a tax return. If the alien doesn't have an ITIN, he or she must apply for one. See Form W-7, Application for IRS Individual Taxpayer Identification Number, for details.
An ITIN is for tax use only. It doesn't entitle the holder to social security benefits or change the holder's employment or immigration status under U.S. law.
CAUTION! All ITINs not used on a federal tax return at least once for tax years 2017, 2018, or 2019 will expire on December 31, 2020. Additionally, all ITINs with middle digits (the fourth and fifth positions) of 88 will expire at the end of 2020. ITINs issued with middle digits of 90, 91, 92, 94, 95, 96, 97, 98, or 99 are expired unless a renewal application was already submitted and it was approved. All expired ITINs must be renewed before being used on your tax return. See IRS.gov for more information.
Adoption taxpayer identification number (ATIN). If your qualifying person is a child who was placed in your home for adoption and for whom you don't have an SSN, you must get an ATIN for the child. File Form W-7A, Application for Taxpayer Identification Number for Pending U.S. Adoptions.
Child of divorced or separated parents or parents living apart. Even if you can't claim your child as a dependent, he or she is treated as your qualifying person if:
The custodial parent is the parent with whom the child lived for the greater number of nights in 2020. If the child was with each parent for an equal number of nights, the custodial parent is the parent with the higher adjusted gross income. For details and an exception for a parent who works at night, see Pub. 501.
The noncustodial parent can't treat the child as a qualifying person even if that parent is entitled to claim the child as a dependent under the special rules for a child of divorced or separated parents.
Note that any link in the information above is updated each year automatically and will take you to the most recent version of the document at the time it is accessed.