A deduction reduces adjusted gross income to determine taxable income. A credit can reduce total tax. A deduction reduces totel income to determine adjusted gross income. A credit can reduce total tax. Question 71 of 81 . sdutniet exjenes deduction that they mey cigim on theit form 1040 ? A deduction reduces adjusted gross income to determine taxable income. A credit can reduce total tax. A deduction reduces totel income to determine adjusted gross income. A credit can reduce total tax. Question 71 of 81 . sdutniet exjenes deduction that they mey cigim on theit form 1040