System Audit
The system audit it often overlooked as most companies think that their external or internal auditor would take care of this, and if they don't then the IT department would make sure everything is okay.
Unfortunately this is often not the case and systems get overlooked on the "if it's not broken don't fix it rule", and while this is an understandable response it sometimes means that the solution is not kept up to date, for example are your systems XBRL compliant?
Also overtime practices move away from the documented processes and in many cases systems are not even documented, leading to other challenges.
A system audit will document your systems and the interaction between them, this can be used in new or additional system procurement, it can form part of your disaster recovery plan or provide detailed descriptions of processes for new staff and management.