Fix VirtualMerchant 'ssl_salestax' errors
This error appears when your VirtualMerchant is incorrectly configured. While your store might charge taxes on orders, the amount that Shopify sends to the payment gateway to be processed isn’t broken down into subtotals/taxes, it’s just a lump sum.
To resolve it, go to Payment Field Setup, make sure that Sales Tax is set to No. Afterwards, run a test transaction to make sure everything’s running correctly.