How must tax they actually pay depends on their overall tax situation, but when you put their SSN on your tax return to claim the credit, the IRS will be trying to match their tax return to yours.
Also, if you paid someone who worked in your home, they are your household employee and you must give them a W-2 and withhold and pay self-employment tax. If they worked in their home, they are self-employed. You don't give them any paperwork, they are expected to keep their own accurate business records of income and expenses.
