ERP workflow without posting process

After a quote is entered onto your site, call the CreateTransaction API and set AvataxTransactionType to either SalesOrder or PurchaseOrder. This will get you a tax calculation based on your shipping address and the customer’s destination address, but it won't record a permanent transaction. You won’t have to do any cleanup for abandoned carts.
After reviewing the invoice entry, call CreateTransaction again with AvataxTransactionType set to SalesInvoice or PurchaseInvoice .
When your order ships, call the CommitTransaction API to mark the transaction as committed. This will prevent accidental changes to the transaction and allow you to include it in a Managed Returns Services tax session.