If you’re an experienced or particularly free-willed trekker, you might want to hike the Classic Inca Trail independently -- no tour operator, no guide, no porter, just you and the trail. That, however, is no longer possible.
Trekking along the Inca Trail without a guide has been prohibited since 2001. According to the official Inca Trail Regulations (Reglamento de Uso Turistico de la Red de Caminos Inca del Santuario Histórico de Machu Picchu), use of the Inca Trail for purposes of tourism must be carried out in organized groups of visitors through a) a travel or tourism agency or b) with an official tour guide.
Inca Trail Agency Tour Groups
For most visitors, this means booking and hiking the trail with one of the 175 officially licensed Inca Trail tour operators in Peru (or through a larger international travel agency with a partnership with a licensed operator).
Tour agencies do all the work for you, at least in terms of organization. They book your Inca Trail permit, they sort out your group (maximum and minimum group numbers vary between operators), and they supply a guide or guides and provide porters, cooks and most of the necessary equipment.
According to Inca Trail regulations, tour operator groups cannot exceed 45 people. That may sound like quite a crowd, but the maximum number of tourists per group is set at 16. The rest of the group consists of porters, guides, cooks etc (you’ll rarely find yourself trekking in a group of 45).
The Independent Inca Trail Tour Guide Option
The closest you can get to hiking the Inca Trail independently is with a lone guide.
This does away with the whole agency side of things, leaving you to organize and carry out your trek (alone or with friends) with an authorized Inca Trail tour guide. The guide must be authorized by the Unidad de Gestión del Santuario Histórico de Machupicchu (UGM) and he must accompany you throughout the trek.
Inca Trail regulations state that any group organized by a single authorized tour guide must contain no more than seven people (including the guide). Support staff is prohibited, meaning you’ll be trekking without porters, cooks etc. That, in turn, means you’ll be carrying all your own gear (tents, stoves, food...).
The process of finding and hiring an authorized guide can be tricky, especially if you’re trying to organize your trek from outside Peru. Most authorized guides are already working for one of the licensed Inca Trail operators, so finding an experienced (and reliable) guide with time to lead a trek can be problematic. Furthermore, it’s much easier to research the reputation of a tour operator than that of an individual guide.