Because of the enormous variety of systems and standards used around the world, predicting the length of the customs clearance process is challenging. If all of the essential documentation are in order, import customs clearance can usually commence while the products are still in transit and before they arrive in the destination country. Many countries have online procedures for submitting customs entries, allowing the items to be released in as little as 24 hours. The time can be prolonged to a few days or even weeks if customs authorities have questions, request further documents, or insist on an inspection of the items. The seller and buyer must work together to submit the proper paperwork to avoid storage fees at the port or airport of arrival.