Tax credits和tax deductions都是减少税收的方式，但它们的作用方式有所不同。Tax credit是直接减少你应付的税款金额，而tax deduction是减少你计算应付税款时所依据的可征税收入。
举例来说，如果你有$1,000的tax credit，那么你的最终税款就会减少$1,000。而如果你有$1,000的tax deduction，这将减少你可征税收入，如果税率10%，那么最终只减少了$100。
Tax credits通常会用income limit
Child Tax Credit:
MAGI <=$400000 jointly $200000 others
Earned Income Tax Credit:
MAGI <= $63,398 jointly $56,838 single (marriage penalty?) inves
Credit for Other Dependents:
AGI <= $438,000 for all (marriage penalty?)
Adoption Credit:
MAGI <= $292,150 for all (marriage penalty?)
Low-Income Housing Credit
No income limit for property owners but requirement for property rents
Premium Tax Credit (Affordable Care Act)
no greater than 133% of the federal poverty line for your family size
Lifetime Learning Credit and American opportunity credit
MAGI <= $160000 for jointly $80000 for others
