You're not going to get a pass for being forgetful if you show up in the mountains or on a lake without all your necessary permits and passes.
And, you won't want to drive all the way back into town to get the pass you need.
Keep all your permits and passes together in a bag and switch it from rig to rig as you need it.
Here's a checklist of some of the permits that are available:
Idaho fishing license - Available from sporting goods stores or online at fishandgame.idaho.gov.
Invasive species sticker for non-motorized boats - Any boat registered in Idaho or another state must purchase and display the sticker to launch and operate legally in Idaho. Nonmotorized vessels except inflatables less than 10 feet in length also must have a sticker. Get more information at parksandrecreation.idaho.gov.
Current registration for your motorboat or sailboat - Registration includes the invasive species fee. (See above website.)
If you're boating in a neighboring state, they also likely require the invasive species sticker for their state, and won't recognize Idaho's.
Current boat trailer registration and plates - Get them at DMV.
Idaho recreation vehicle registration - Get them at DMV or county assessor's offices. For details, go to itd.idaho.gov/dmv.
Idaho Off Highway Vehicle sticker for your motorcycles or ATVs - For details go to parksandrecreation.idaho.gov and click on the ATV/Motorbike icon.
Campground reservation printout - When you make a reservation you get a confirmation.
Senior pass for federal recreation sites - To get the senior discount, you must get your pass in advance at store.usgs.gov/pass/general.html.
Idaho State Parks Passport - Allows entry into all state parks without paying the day-use fee. Go to parksandrecreation.idaho.gov.
Group passes - National forest regulations require gatherings to get a special-use permit for use of national forest lands. Under the regulation, a permit is needed for an activity that involves a group of 75 or more people. Check with local U.S. Forest Service offices.
Firewood permit - If you're bringing back a load of firewood after your campout, get a permit from Forest Service offices or get a list of vendors from each forest headquarters. For Boise National Forest, go to fs.usda.gov/boise.