Working Families Tax Relief Act of 201 7 This bill amends the Internal Revenue Code, with respect to the earned income tax credit, to: (1) increase the credit and reduce the phaseout percentage for taxpayers with no qualifying children, (2) reduce from 25 to 21 the qualifying age for individuals with no children, (3) revise eligibility rules relating to married individuals living apart and qualifying children claimed by another family member, and (4) repeal the denial of such credit for taxpayers with excess investment income. This bill modifies the child tax credit to: (1) increase the amount of the credit and the portion of the credit that is refundable for taxpayers with children under the age of six, and (2) require the dollar amounts of the credit to be adjusted for inflation after 2017.