[header] How to record business miles [title] Record your odometer readings. [step] The most straightforward way to record business miles, and the one preferred by the irs, is to write down your car's odometer readings when you begin and end the trip. The difference is your mileage. 
[substeps] This will get you the most exact mileage for your trip. While writing down your odometer reading at the beginning and end of every trip takes effort, eventually it will become a habit.