The requested refund amount for the tax or shipping tax is too high. For help on how to proceed, see http://sellercentral.amazon.ca/gp/help/25201
This error occurs when the refund amount you are requesting for the tax or shipping tax component of an order exceeds the amount that can be refunded. Common reasons why your requested refund might be to high include the following:
For example, if a customer pays $2 for shipping tax, you can refund up to $2 toward the shipping tax component of the order. If you refund $1.50 of the shipping tax, the customer's shipping tax balance is $0.50. Any future refunds for the shipping tax cannot exceed that $0.50 balance.
To view the current balance for any component in an order, you can search for the order using the Search Orders feature in Seller Central.
To resolve this error, please resubmit your data with a refund amount that is less than or equal to the customer's current balance.