Tell the auditor early and keep a dated change record. Explain what changed, which controls were affected, when the new process began, and where evidence from both versions is stored. A move to a new identity provider, for example, can affect access lists, approvals, and termination evidence. Preserve the old records before shutting the system down. Update your system description and control documentation where appropriate. The auditor will assess the effect on scope and testing; a change does not automatically mean the whole period must restart. Agree on the evidence handoff before the migration rather than during fieldwork.
Related: SOC 2 audit and compliance hub.
Further reading: AICPA SOC 2 reporting guide overview.