20,000 employee employer going live 7/1/21 - hourly, salary and unionized employees

Summary

Asking for tips for go live and some specific payroll audit information as well - Oracle Cloud Fusion

Content

Hi, we are a school district with 20,000 employees represented by 5 unions. We have hourly and salaried employees. We have significant turnover, frequently hiring, and offboarding. We have also just started using Taleo and we will bring on ADP when we go live on 7/1 to distribute pay and handle quarterly and annual taxes and W2s. We have been working with consultants on discovery and implementation. We would appreciate tips, lessons learned, etc but also specifically can anyone tell me how you do a pre-audit during the payroll cycle to be sure payroll is processing as expected?  Do you make