When trying to calculate tax, you receive the error message: "An address is incomplete or invalid." However the error does not happen if another user processes the transaction
First check both the Company/Location/Warehouse address and the Customer's ship to address.
Make sure a full address is included (street name, City, State, ZipCode, Country Code) and in the correct fields in Quickbooks
If all addresses are correct and this issue only occurs for one user, or one type of user, in Quickbooks, the address is being dropped when posting due to insufficient user permissions to the Inventory Site List in Quickbooks.
Please upgrade to the latest AvaTax connector (version 80 and higher)