I moved to Hong Kong last Febrary and my son lived with me there for more than 6 months in 2019. Is he eligible as a 'qualifying dependent' to claim tax credit?

Yes, to claim an exemption for your son, you must be able to answer "yes" to all of the following questions.

• Are they related to you? The child can be your son, daughter, stepchild, eligible foster child, brother, sister, half brother, half sister, stepbrother, stepsister, adopted child or an offspring of any of them.
• Do they meet the age requirement? Your child must be under age 19 or, if a full-time student, under age 24. There is no age limit if your child is permanently and totally disabled.
• Do they live with you? Your child must live with you for more than half the year, but several exceptions apply.
• Do you financially support them? Your child may have a job, but that job cannot provide more than half of her support.
• Are you the only person claiming them? This requirement commonly applies to children of divorced parents. 

This link Rules for Claiming a Dependent on Your Tax Return has information you may find helpful.

Thanks for your prompt reply. From the link below, I found the IRS required the child

"must have the same main home as you (or your spouse if filing a joint return) in the United States for more than half of the tax year."

https://www.irs.gov/credits-deductions/individuals/earned-income-tax-credit/qualifying-child-rules

 

However, my child lived with me in Hong Kong outside the USA, is he still eligible?

Thank you very much

Eric 

You can claim him as long as he is a US citizen, resident alien, or citizen Canada or Mexico. The home does not have to be in the United States.