The tax credit for a qualifying child dependent under age 17 is up to $2000. However, the credit can only reduce your tax owed and can't be refunded if you don't owe tax. That is to say, you get get a refund that is more than what you paid in as withholding. The Additional Child Tax Credit can pay you up to $1400 in your refund even if you owe no tax, but you must have income earned from working. Turbotax will figure this all out for you.
For a qualifying child over age 16, or a qualifying relative or "other" dependent, the credit is up to $500, but it can only reduce your tax, it can't be refunded if you owe no tax.
