Many phaseouts create significant marriage penalties — or bonuses — because the phaseout range for married couples is less than twice that for single tax filers. (taxpolicycenter.org)
Many phaseouts are indexed for inflation so that the phaseout ranges remain fixed in real terms. (taxpolicycenter.org)
For married couples the phaseout range begins at MAGI of $ 160,000 and the credit is completely phased out at MAGI of $ 180,000. (taxpolicycenter.org)