When the system fetch the tax code for order lines it first check whether there is any RetailerTaxCode.

- If there is a retailer tax code that tax code and tax percentage rate is used as the line tax code and line tax percentage rate.

- If the retailer Tax code is not specified then we fetch the item tax code and item tax percentage rate (As it is specified in the AC system)

- If the Item Setting Always use Default Tax Code is set to true the system always use the tax code and the tax percentage rate specified in the item settings.