Keep your receipts.
I don’t know a single person who started a business so that they could have mounds of receipts that they needed to keep in order to protect themselves from the government.
No one likes to do this, but you absolutely must.
When you make a purchase, write a note on the receipt about what the expense is about, and take a picture. If you do nothing else, at least take these steps.
If you want extra credit, you can upload to DropBox, and file it by month.
If you want to be a National Merit Receipt Keeper, you can save it in Quickbooks Online with the expense. There is a super easy way to do this, that I would be happy to tell you about.
I always ask my clients if they would rather have me after them or the IRS.