We sell nationally via Amazon Marketplace, and because our parent company has locations in all 50 states, we are required to collect taxes on all 50 states. 

When we get an order from Amazon, it already has the correct sales tax for State, County, City, and Special Districts included as one amount. 

We do not have these set up as tax schemes, we only have the state levels. So when the order arrives, at SO/Sales Order Entry the tax schedule is loaded for the state, and the calculated amount is overridden and replaced with the correct amount from the invoice. However, when we go to invoice, the amount that was entered is deleted, and a new, incorrect amount is calculated based on the tax schedule the customer is set up for. 

My questions are as follows:

1) For those of you who sell nationally, how do you handle taxes for all locations?

2) Why is the sales tax amount entered originally in the order not being followed to the invoice, but instead recalculated at the time of invoice? Is there any way to fix this?

Thank you in advance.