How do I collect my child's stimulus checks if I never received them?

You will need to file a 2020 tax return claiming your child as a dependent.  If your child age 16 or under qualifies for a stimulus payment, a Recovery Rebate Credit will be added to your return in that amount.  To qualify the child must have a valid social security number and meet the qualifications for the Child Tax Credit outlined below.  

• The child must be younger than 17 on the last day of the tax year, generally Dec 31.
• The child must be the taxpayer’s son, daughter, stepchild, foster or adopted child, brother, sister, stepbrother, stepsister, half-brother or half-sister. An adopted child includes a child lawfully placed with them for legal adoption. They can also include grandchildren, nieces or nephews.
• The child must have not provided more than half of their own support for the year.
• The taxpayer must claim the child as their dependent on their federal tax return.
• The child cannot file a tax return for the same year with the status married filing jointly, unless the only reason they are filing is to claim a refund.
• The child must be a U.S. citizen, a U.S. national or a U.S. resident alien.
• In most cases, the child must have lived with the taxpayer for more than half of 2020.

Here is a link with more information on the Recovery Rebate Credit.