This is required if you plan to go via the Spiti Valley (optional on the June Run, unavoidable on the September Run). despite it being optional in June, you should definitely try and go that way if you can though as it's quite simply the most adventurous part of one of our most adventurous events.
Shimla to Leh (September)
Step 1 - Get a letter from a registered travel agent in Himachal Pradesh stating that they are sponsoring you and a permit can be issued. You will also be required to produce a copy of your passport, visa, three passport sized photographs, an itinerary of your travel plan (you won't be oblied to follow this itinery) and about 300 rps.
Step 2 - Go to the District Magistrate office which is on the west side of 'the ridge'. Find the permit issuing office. Be aware that the office is closed on holidays (which are frequent) and at random times throughout the day.
Step 3 - Fill out the paperwork and submit the documents you have for processing. They'll tell you to return later to pick it up.
Step 4 - Pick up your permit. Whilst it can take 2 hours you'd be better off setting aside the day for it and then count yourself lucky if its over sooner - be prepared to get messed around a lot - 'come back at 11am' 'come back at 1pm' 'the officer has gone for lunch' 'come back at 4.30pm' etc etc etc. It will be valid for 10 days to 14 days as standard.
You can pick it up from Reckong Peo en route. At Reckong Peo they are issued at the DM office at Khwangi Road. The process is typically 15 - 25 minutes long in total. You may not need your passport photo's either as they have a digital camera and printer. There are a few travel agents in Reckong Peo such as 'The Monk Travels' that can get the permit on your behalf for about Rs. 200 per person. Bear in mind though that the office is usually open between 10:00 and 16:30 so if you come outside of these hours you'll have to hang around until it is next open.
The check-post is just after Reckong Peo that will prevent you going further without this permit.
Leh to Shimla (June)
Unfortunately it is not possible to get a Spiti valley permit in Leh as it can only be issued within the borders of the state of Himachal Pradesh. You will need to find the District magistrate office in Keylong or the additional deputy commissioner in Kaza. You will need the same paperwork as in Shimla above. Finding a travel agent to do the work for you in either of those towns is usually advisable simply to take the hassle out of it.
All the above offices are closed on Sundays, the second Saturday of each month and on national holidays.
Once you have the permit get 5 or 6 copies printed as the checkpoints will often want to keep a copy.
The permit is valid for 10-14 days so you shouldn't have to worry about it running out.
To reiterate, it's well worth getting. The Spiti Valley is the bit that really separates the boys from the slightly bigger boys.