Hi @mmff, regarding auditors they should be as independent as possible, which usually means they should only do audit work (tax work may also be done which is ok), but providing consulting beyond this needs to be disclosed and you will note that the accounts show the remuneration of the auditors.
Things to look out for is not so much changing auditors but how often. If they change every few years then it smells like they are opinion shopping for their accounts and unless this is well explained, then it's a red flag. Also if they are paid way above normal rates, then it begs a question.
Likewise and as investors in Corporate Travel Management have just found out, having the same auditor for a very long time can be a problem also. If the auditor has made a mistake they are unwilling to make adjustments and let the misstatement carry forward (or may be "too close" to management), where as a new auditor will have no such historical reputation to protect and make sure everything is reported correctly.
Listed companies have their own accountants, the CFO manages the accounts and reporting. The only reason auditors are used is to ensure an external, independent party has checked that the accounts are prepared properly, the resources and skills to prepare accounts should exist in the company.
I am an accountant & CFO, but was never an auditor - been through a lot of audits, but not for a listed company, but the process is much the same.
Good question, if your not an accountant or in finance it's an area that few understand or look into - probably because it's far to exciting for most ;)