Saving Those Receipts For Tax-Time:

As for the mileage driven I've been told to just write it down on a calendar daily and this also will pass as an official document

That's pretty much what truck driver do but they use a more official form. It's called a log book if you want to start using one. You can confuse the h*ll out of most people when looking at one filled out. When I hauled campers I would get back home from a trip and be finishing up my log book and it would "legally" say I was still in Ill. or Ky. 300 or 400 miles from home. lol