If I claim my parent's caregiver expenses as a medical expense what tax form do I provide to a caregiver that assist me?

We pay our caregivers as employees. When we first hire a caregiver, we ask him or her to fill out a W-4 so that our accountant knows what taxes need to be withheld. Instead of doing our own payroll, we have hired an accountant to make sure we get the amounts correct.