Negative prices for deposit system

[Trammelant]

Dear,

Can items have negative prices? In Belgium and across Europe, certain events require a fee for cups that patrons use to drink from. However, when they return the cups, they receive a refund. In this scenario, implementing a deposit system where negative prices are assigned to the item "deposit" would facilitate the refund process for returned cups. 

[Ramona]

Thanks for this question i have the same problem in switzerland, i hope someone can help us...