Cross-charged costs analysis

Hi all,
as an outcome of crisis management, I've got a task to analyse cross-charged opex costs within my company. Basically other departments charge us for IT, accounting and HR services and I should look at those and review them.

As I'm not a financial analyst and this task was given to me just due to the current situation, could you please give me some tips how to perform this analysis? How to start, what to focus on in my outcome, etc.?

Thanks a lot in advance!

Patrick