Sometimes goods have to be licensed to be exported. This means that the seller is obliged to apply for export clearance from the relevant government. Usually, the government department will issue an Export licence which is a legal document indicating the goods can be exported whether temporarily or permanently.
Certain receiving countries are embargoed and the list changes according to government policy. If you neglect to check this and the goods are exported illegally, you and your company could be liable to fines and/or prosecution. Export controls are used to prevent the export of goods and technologies that, if sold abroad, would run counter to government policies. For instance, there are controls stopping the proliferation of weapons of mass destruction. If you need to apply for a licence, don't forget to allow for the time it will take (perhaps up to a month) when asking the customer to draw up a letter of credit.