Can my retailer backdate my charges?

Yes, if customers have paid less than they owe for water in the past, the retailer has the right to back-bill them for a certain period, which is usually up to 16 months. However, in specific situations where there is a disagreement between the retailer and the wholesaler about the charges owed, or both parties agree that the calculations were incorrect, the retailer can back-bill the customer for a longer period, up to a maximum of 24 months. On the other hand, if a customer has overpaid, there is no time limit for them to receive a refund. 

Companies charge you for the services they provide and there is no time limit on collecting these charges.