tax credit: a sum of money that is taken off the amount of tax you must pay
指可以直接抵免应纳税额，而不是应税收入，中文叫“抵税额”
tax deduction: represents an expense incurred by a taxpayer that is subtracted from gross income and results in a lower overall taxable income
指纳税时可以减少报税的收入金额，以计算应纳税所得额，例如月收入是10000元，报税时可以报8000元，从而降低纳税金额。中文叫“扣税额”。