You can’t hike the trail independently so you must book with an outfitter.
They arrange the permits, which cost $99. You must get your permit in advance through the outfitter, so they will usually ask that you wire money to them( just a few agencies accept credit cards for either the deposit or final payment) so that they can pay for the permits. You will also send the name on your passport and passport number to them. When you start your hike, you will show your passport at a station and the names on the permit and your passport must match. This prevents agencies from buying permits on speculation. Permits are non-transferable, so there is no refund if you have to cancel.
Check this site for permit availability. NB Please be aware that although it sounds as if this is a place to make reservations, and it is, this site belongs to an outfitter, which we have no personal knowledge of and don’t wish to imply that we are endorsing them because we are using their permit engine. Usually the government has a site and that is down. Until that site is functioning, we will use this search tool. Check in the outfitter sections to see what others have to say about this company. We did see them along the trail during our hike.)You can also check this official Peru government site (In Spanish)for availability