Your import duties will be calculated using the value of your shipment as estimated by customs officers and the shipment's grouping on the harmonized tariff schedule. The value of the shipments includes the price paid, commissions incurred from the purchase, royalty fees, license fees, packing costs, and the value of assists (specialized machinery or molds used in the manufacturing process). Your duties are then determined by using the tax rate specific to items of your shipment type on the US Government's Harmonized Tariff Schedule.
Tariffs may vary by origin as well. For example, liquor (alcoholic beverages containing over 20 percent but no more than 50 alcohol by volume) is taxed at a standard rate of 8.4 cents per kilogram and an additional 1.9% of total value. However, this fee is waived when the items are coming from certain locations (including Canada and Singapore).
If any of your filed documents are inaccurate, you will need to file corrected documents before you can pay your duties.
Your duties are due within ten days of the receipt of your initial import documents.
Your customs broker should be able to help you estimate the cost of your duties before you import the goods.