I’m going to start the new year with a few reposts of essential information. Yes, you do need to keep a mileage log:

Today is the first business day of the new year. You may have resolved to keep good records this year (at least, we hope you have). Start with keeping an accurate, contemporaneous written mileage log.

Why, you ask? Because if you want to deduct all of your business mileage, you must do this! IRS regulations and Tax Court rulings require this. Written is defined as ink, so that means you need a paper log.

The first step is to go out to your car, and note the starting mileage for the new year. So go out to your car, and jot down that number (mine was 40,315). That should be the first entry in your mileage log. I use a small memo book for my mileage log; it conveniently fits in the center console of my car.

Here’s the other things you should do:

On the cover of your log, write “2014 Mileage Log for [Your Name].”

Each time you drive for business, note the date, the starting and ending mileage, where you went, and the business purpose. Let’s say you drive to meet a new client, and meet him at his business. The entry might look like:

1/2 40315-40350 Office-Acme Products-Office, 1234 Main St, Las Vegas
Discuss requirements for preparing tax return, year-end journal entries

It takes just a few seconds to do this after each trip, and with the standard mileage rate being $0.56/mile, the 35 miles in this hypothetical trip would be worth a deduction of $20. That deduction does add up.

Some gotchas and questions:
1. Why not use a smartphone app? Actually, you can but the current regulations require you to also keep a written mileage log. You can transfer your computer app nightly to paper, and that way you can have the best of both worlds. Unfortunately, current regulations do not guarantee that a phone app will be accepted by the IRS in an audit.

2. I have a second car that I use just for my business. I don’t need a mileage log. Wrong. First, IRS regulations require documentation for your business miles; an auditor will not accept that 100% of the mileage is for business–you must prove it. Second, there will always be non-business miles. When you drive your car in for service, that’s not business miles; when you fill it up with gasoline, that’s not necessarily business miles. I’ve represented taxpayers in examinations without a written mileage log; trust me, it goes far, far easier when you have one.

3. Why do I need to record the starting miles for the year?
There are two reasons. First, the IRS requires you to note the total miles driven for the year. The easiest way is to note the mileage at the beginning of the year. Second, if you want to deduct your mileage using actual expenses (rather than the standard mileage deduction), the calculation involves taking a ratio of business miles to actual miles.

So start that mileage log today. And yes, your trip to the office supply store to buy a small memo pad is business miles that can be deducted.