When a company keeps SAP HCM on-prem for payroll and adopts SuccessFactors as the new HR core, a natural tension appears: two systems can describe the same person, but not always from the same operational moment.
Mistake 1: not defining the master system by entity
Saying “SuccessFactors is the master” is not enough. It may be the master for identity and position, while SAP HCM still governs payroll, company codes, local rules or historical data.
Mistake 2: ignoring effective dates
SuccessFactors works with effective dating. An integration that only reads the current state can miss future movements, retroactive changes or corrections that impact payroll.
Mistake 3: not designing reconciliation
Reconciliation is not a nice report at the end of the project. It is an operational capability to compare counts, keys, statuses and differences by entity.
Practical rule: if you cannot explain what happens with a rehired employee, a retroactive change or a future termination, the integration is not production-ready yet.