Customs brokerage involves facilitating transactions with customs regarding importation of merchandise. A customs broker's license is required to conduct customs business. Some transactions not requiring a license include importing solely for personal use and transporting cargo. Various types of customs entries exist including formal consumption for permanent imports, informal consumption for low value shipments, and temporary import bonds for one year imports. Transportation entries allow cargo to be transported within or out of the customs port without duty. Warehouse entries provide temporary storage for up to five years. Foreign trade zones allow duty deferral and manufacturing of goods. Certain goods like American exports can be declared duty free on return. Low value and instruments of trade are exempt from entry. Ship spares can use transportation or