If your 2018 Child Tax Credit is less than your 2017 credit, it's probably because:
- One or more children celebrated their 17th birthday in 2018, or
- One or more children have an ITIN instead of a Social Security number.
Starting in tax year 2018, children with ITINs no longer qualify for the Child Tax Credit, but instead may qualify for the new $500 Credit for Other Dependents ("Family Tax Credit").
Other, less common reasons your 2018 Child Tax Credit is less than your 2017 credit include:
- One or more children lived with you for less than half the year in 2018 but lived with you for half the year (or more) in 2017;
- One or more children paid more than half of their own expenses in 2018, but didn't in 2017;
- Your 2018 AGI increased to $400,000+ (joint filers) or $200,000+ (all others).