On the VNPost Invoice Information Portal, explain what information is required to successfully search for an invoice using its lookup code. Specifically, describe the two necessary pieces of information and clarify if any of them are dynamic or change with each attempt.
Navigate to 'https://hoadon.vnpost.vn/' Locate the 'Tìm kiếm hóa đơn' (Search invoice) form. Identify the purpose and nature of the 'Nhập mã tra cứu hóa đơn' (Enter invoice lookup code) field. Identify the purpose and nature of the 'Mã xác thực' (Authentication code) field, noting its association with a captcha image. Formulate an answer that explains both required inputs and the dynamic aspect of the authentication code.
State that the 'invoice lookup code' is required. State that an 'authentication code' is required. Explain that the authentication code is dynamic and derived from a captcha image. Confirm that both the invoice lookup code and the dynamic authentication code are necessary to perform a search.