By using this feature, the add-on lets you read the document destination ship-to address from custom UDFs instead of using the default native SAP address fields. This is mostly useful when using third party integrations that creates documents populating the ship-to address into alternative UDFs instead the default SAP address fields. The configuration from Avatax Settings include different options:   Read and send address from custom UDFs This checkbox must be enabled to activate the feature. If unchecked the solution will always read the ship-to addresses from the default SAP fields.   Read if this UDF has a value This feature let's you use a UDF as a flag to indicate the solution if must read the address from the alternative fields for that specific document. If the configured flag UDF value is empty (no value), then the solution will read the address from the default SAP address fields. If a value is present in the flag UDF, it will read the ship-to address from the configured alternative UDFs. If you want to read the address from UDFs for all documents, then just need to leave this flag UDF name empty in the configuration, and the solution will not evaluate it and will always read from UDFs.   Custom UDFs at line level This checkbox let's you indicate if the custom UDFs for the address parts: line, city, state, zip and country, are defined at the document header level or at the document line level. When unchecked, the solution will look for the UDFs at header level. If checked will look the ship-to address UDFs at line level, for each line.   UDFs In this section you need to complete the UDF name for each one of the address components. Make sure to complete the UDF name as is defined in the database: this is with the U_ prefix and it's case sensitive.