If you have a shipping address that's outside of the UK (or EU) then import duties and taxes may be applied by your local customs department. Examples of this include the USA for orders over $800 (more information here), Canada for orders over $20 CAD (rates vary by state) and Switzerland (currently charged at ~8%).
Unfortunately, we have no control over these charges and we can't tell you what the cost will be in advance as customs policies and import duties vary widely from country to country, and the value of the parcel. It might be a good idea to contact your local customs office for current charges before you order, so you are not surprised by charges you were not expecting.
It is a legal requirement that we declare the full value of the contents of all packages, so please do not request that we send a parcel without this.