There are times when the only way to lower your tax liability is to have more taxes withheld from your paycheck or retirement. As children leave the home, your tax liability begins to increase. After a child turns 17, and it doesn't matter what time of the year this happens, you no longer qualify for the Child Tax Credit of $1,000.This affects the amount of taxes you will owe. Once the children leave the home or turn 19 and are not full-time students or they work, if they make more than the exemption amount ($3,900 for 2013), they cannot be claimed on the parent's tax return. This can greatly affect the amount of taxes you will owe.