In serving on a Dean's office sub committee on Standard Operating Practice there were long discussions regarding what is required as documentation for Retros. While I find that including the background information as to where the individual was paid, why the change is being made, who requested the change, where request was made i.e. email, finance meeting etc. I was surprised to learn from another CA that a recent audit of a sponsored project there was a request for documentation of the calculations on how the amount of the retro was determined.