I have recently discovered a customer who makes deposits of cash almost daily. They are not large amounts. In researching, I have seen many checks written to a large retail store for even amounts. I dug a little deeper and found that he works for the store. It appears that he will write them a check, they cash it, he brings the cash to the bank, the checks are held and ran later. We have spoken with him and he says this is a perk for working for the company.Not sure how that could verified. We are needing advise on what we should actually do at this point. Is a SAR justified? Would we mark the box for (other) under suspicous activity?

How does his balance look?

If he's in danger of overdrawing (the cash deposits are getting to the bank just in time to cover the checks), then he appears to be running a cash kite, and using his influence over when the checks are processed by the store to keep it afloat.

Worry about the SAR after you close the account. Doing so will establish that he's borrowing money from the store instead of you.