When create a Credit memo, I don't want to credit the Shipping cost, So in the field Refund Shipping, I just write 0. but system still refund the tax part of the shipping cost.
For example, if the shipping cost is 7 USD, and in the credit memo i write 0 in Refund shipping, the system will still refund 20% of the tax which is 1.4 USD.
Any ideas why this is happening?