I also would like to comment that I can't believe that you (at LCC) have to enter an inventory record at the beginning or end of the flight. The caterer is responsible for accuracy of the beginning inventory. If the company does not trust you, they should be checking the carts immediately after they are removed from the a/c, then compared to the sales record in the HHD.
Evidently your company does not trust your caterer or you. I know that at AA, you see evidence all the time of caterer pilferage--half-empty minis in the insert, "locked" carts being boarded with the lock ties already torn off. Fortunately, f/as are not held responsible for this--particularly if we document on the catering papers that the cart was unlocked when boarded and turn in the papers.