The Inca Trail regulations started in 2004 the 4 day Classic Inca Trail has been limited to 500 people a day, this is including the guides, porters and the trekkers; between those 500 people starting every day from km 82 only about 200 people are the actual trekkers, the rest are porters, and 250 travelers are allowed to start the hike every day from Km 104, which is the short Inca Trail trek; both trails are open from March to January, but February is close for maintenance and cleaning.
Was a good idea to put Inca Trail regulations, because the Inca Trail tours go through the protected area named Historical Sanctuary of Machu Picchu and that is why trek permits are required to hike any of the Inca Trail treks, the Peruvian government office is the institution in charged annually selling all the trek permits for the 4 day classic Inca Trail and the 2 day short Inca Trail hike. according to the Inca Trail regulations trek permits are sold at the end of each season for the next season, so we highly advice trekkers to book Inca Trail spots way in advance.
Only authorized tour guides and travel companies are allowed to book the Inca trail hiking permits, this applies for the Classic 4 day Inca Trail trek and the short Inca Trail tour. On the 4 day Inca Trail hike is permitted camping activities but in the short Inca Trail to Machu Picchu camping is not allowed, so hikers need to walk the distance of 13km in about 6 hours until to arrive to Machu Picchu through the Sun gate and take the bus to Aguas Calientes town to stay in a hotel. All these Inca trail regulations are applicable to the 4 day and 2 day Inca Trail tours.
The Inca Trail regulations will be even more strict, due the importance of the Historical Sanctuary for the humanity as it is a world heritage.