We do not offer the option of pre-paying for duties and taxes on international shipments so you may be billed for duties if you ship your order outside the United States.
All international mail shipped into Canada is subject to review by the Canada Border Services Agency (CBSA). The CBSA determines if any duty and/or taxes apply. This means you may receive a bill from the CBSA after you receive your order. For more information on Canada duties, check out this link: http://www.cbsa-asfc.gc.ca/import/courier/menu-eng.html
All mail shipped to the UK from outside the E.U. may be subject to VAT, Customs Duty, or Excise Duty. So, you may receive a bill after you receive your order. For more information on UK duties, check out this link: https://www.gov.uk/goods-sent-from-abroad/overview