Time Posting Data Analysis

I work in a professional services company and would like to get some analytics on how discipline the fee earners post their times to the system may have an impact to the revenue.

One area that I am thinking of is to see if there is a correlation between how late the time entry is posted after the work was done and whether that time entry is being written off (i.e. does not make it to the bill to the client).

Is this a reasonable thing to analyse? If so, what technique should I be looking at to analyse this, e.g. correlation, regression, clustering, etc?

If there are other things that I can analyse as well, please let me know.

I am quite new to this data analytics/mining/science so please guide me. I have some understanding of R language which will be my primary language in analysing the data (and SQL to get the data).

Thank you.