I use Google Sheets. It's convenient because you can access from your phone and I can add information like mileage on the fly. I color coat everything by company which makes it easier to track. Don't forget you can go back to mystery shopping companies and collect your reimbursement information as well. I keep a combination of digital and paper records for everything that I am getting paid for monthly.
As an example for November, I print out my month end information from Sheets that has ms/company, store, address, mileage, Pay, reimbursements, expenses/tolls, total mileage driven, and total mileage reimbursements (IRS) and then I go to each Mystery shopping company I worked for that month and I put in November 1, 2025-November 30, 2025 and I expand each shop to show pay and reimbursements and print that off and put that in my "year end binder for 2025. "
I also put any receipts in that binder for expenses I have during the month and then I place my hard copies that I take with me in the field in a file cabinet that has a printout of whatever I have as evidence that I was there at that time at that place such as a receipt, photo of the business, business cards ect. to establish I was there at that time and place. I'd rather be over prepared then under prepared.