If you want Initial Setup & AvaTax Configuration in Odoo-9 follow the below steps->
Step-1 Install Ava Tax Modules
Step-2 Setup > Installed Modules > Search for AvaTax Click Install button
Step-3 Accounting > Configuration > AvaTax > AvaTax API Click Create button
Step-4 Fill out the form with Company Code, Account Number and License Key provided to you by Avalara
Step-5 Accounting > Configuration > AvaTax > Exemption Code
Step-6 Accounting > Configuration > AvaTax > Product Tax Codes
Step-7 Accounting > Configuration > AvaTax > Shipping Rate Configuration
Step-8 Accounting > Taxes > Taxes >Select AVATAX from the list view
Step-9 Sales > Configuration > Products > Product Categories Click Create button
Step-10 AvaTax Properties > Tax Code, Select the desired Tax Code
Step-11 Sales > Products > Products >Click Create button
Step-12 AvaTax Properties > Tax Code
Step-13 Sales > Customers >Click Create button
Step-14 Enter Customer Address Select the AvaTax tab >Click Validate button
Step-15 AvaTax Module will attempt to match the address you entered with a valid address in its database. Click the Accept button if the address is valid
Step-16 If the customer is Tax Exempt, uncheck the box Under Tax Exemption > Is Tax Exempt Select the desired Tax Exempt Code from the dropdown menu
Step-17 Accounting > Customers > Customer Invoices >Click Create button Step-18 AVATAX Click Compute Taxes
Step-19 Validate Invoice >After the taxes have been computed click Validate button
Step-20 Register Payment >To complete the invoice click Register Payment button
Step-21 Complete the Pay Invoice window >Click Pay button to finalize the Customer Invoice
Step-22 Accounting > Customers > Customer Invoices >Select the invoice you wish to refund >Click Refund Invoice button
Step-23 Create Refund Invoice >Under Refund Method select Create a draft refund from the dropdown >Click Create Refund button
Step-24 You will be taken to the Customer Refunds list view
Step-25 Select the Customer Refund you wish to refund >Review the Draft Refund and click Validate button
Step-26 Click Register Payment button to complete refund
Step-27 Complete the Pay Refund window >Click Pay button to finalize the Customer Refund
Step-28 Create New Sales Order > Sales > Sales > Sales Orders
Step-29 AVATAX Click Compute in the subtotal section of the page