Depends on jurisdiction. https://www.gov.uk/online-and-distance-selling-for-businesses https://www.gov.uk/online-and-distance-selling-for-businesse... might be

Depends on jurisdiction. https://www.gov.uk/online-and-distance-selling-for-businesses https://www.gov.uk/online-and-distance-selling-for-businesse... might be handy for UK citizens as a starting point.