This is an error generated in Walmart's system (this could be Walmart USA, Walmart Canada, or Sam's Club) regarding a problem in the Allowance or Charge information either for an individual line item, in which case it would be on the Item tab, or for the whole invoice, in which case it would be on the Summary tab. The problem is in the Allowance or Charge code that you have indicated. This refers to the option you would have selected from the drop-down menu of Allowances and Charges. This error could be due to indicating an Allowance, but selecting from this menu an option that can only be a Charge, or vice versa. For example, the "Freight" option can only be sent as an Allowance and cannot be sent as a Charge. You should double-check that you are selecting Charges if you are adding to the invoice total, and selecting Allowances if you are subtracting from that total.