In early 2016 the new planning guidance for huts was launched. Huts are now a special category in Scottish planning - to get permission within this category you have to meet the conditions laid out in the guidance. The key points are that a hut is small (less than 30 square metres, built from low impact materials, mostly off-grid and designed to be removable leaving little trace at the end of its life. A hut must not be a person's main residence.
The guidance document is attached below. If you have any questions about planning, post them here.