Complex sentence: Bottom of basket loss (BOB), occurs when an item is placed on the lower tray of a shopping cart and the cashier forgets to check the lower tray for items, resulting in the item not being paid for.
Split into simpler sentences: Bottom of basket loss (BOB) occurs when an item is placed on the lower tray of a shopping cart. The cashier may forget to check the lower tray for items, resulting in the item not being paid for.