Yes, your dependent's income is added to yours when determining household income for the Premium Tax Credit. TurboTax will add their entire income for the year if they are claimed as your dependent. If your child moved out and is no longer your dependent, you may allocate the health plan between both of your tax returns and you would no longer claim their income to determine your Premium Tax Credit.
Your dependent's MAGI that you are reporting for the Premium Tax Credit does not impact any other area of your return or your MAGI.
