E1 HCM and Payroll without Vertex

My organization only uses JDE E1 to calculate gross, benefits, and accruals. We do not calculate tax deductions or any other miscellaneous deductions. We would like to uninstall Vertex, but we are uncertain how this may impact the Employee Master because our interface needs the employee withholding information. 

I believe that the National/Fiscal Data and the Tax Override screens are standard JDE programs that can still be accessible without Vertex as long as the employee is coded with the US country code. Is this a correct statement?