Indeed.

Also keep in mind functions are directly available to any sql statement, not only from within a stored procedure.

Also keep in mind you need to provide the actual schema for the function

Select [Company Name],Patient,Visit,[Visit Date],[Insurance Company],

dbo.InsPolicyVal(A.Visit) -- this is the function which should return value

from [Medical Visit] A ON H.Patient = A.Patient INNER JOIN

[Payment Policies] C ON A.[Insurance Policy] = C.Policy INNER JOIN

[Medical Policy Link] D ON C.EmployerInsuranceLink = D.ID INNER JOIN

dbo.[Insurance Companies] E ON D.[Insurance Company ID] = E.[Insurance Company]