I got fucked by having one of those. I now work in Admistration due to the experience I got defending myself.
Give it back.
Make the A/P/ Purchasing dept create a Purchase Order, signed by the responsible party for everything. A signed authorization for every purchase.
Do not spend money not authorized.
ORRRR Get a title in the company and the raise authorizing you to spend money.
Keep copies in hard currency (paper) on every transaction.
Bankers boxes exist for a reason.