An important part of maximizing the profit from your own business – no matter how small – is to be smart with taxes. If you are running a side business on top of your day job, you may be paying around 50 cents of every dollar made towards taxes. This means, that for every $1 in tax deductions you find, you are keeping an extra 50 cents in your pocket.

One of the more tedious tax deductions for self-employed folks is deducting transportation expenses. The simplest way to claim this deduction for those without vehicles used solely for business is to track the number of miles driven for business use. (You can also record actual automobile expenses like gas and maintenance, and pro-rate.) The IRS just announced yesterday that the standard mileage deduction will be 58.5 cents/mile for all business miles driven for the last half of 2008, up from 50.5 cents/mile.

From above, this means that for every single business mile you deduct, you might save around 29 cents. Deducting just 100 miles per month would save you around $350 over a year. Put another way, not tracking 100 miles a month will lose you $350 a year. There are many complex rules for what constitutes eligible business travel, but it can be worth asking your accountant or reading up. Here are some examples:

• Driving to the office supply store to make business purchases.
• Driving from your home office to an external location meet a client.
• Driving to the bank to deposit checks or make other business transactions.
• Driving to pick up mail from your UPS Store or P.O. Box.
• Driving to the post office to send business-related mail or buy stamps.

Many times, you might do this stuff without a second thought. But with gas costs so high, I would argue that we need to recoup whatever we can get. Trust me, these miles can add up quickly!

How do I properly track such mileage? At most office supply stores you can buy a mileage logbook. Or, simply start up a spreadsheet program and create these columns: date, purpose (bank, etc.), odometer start value, odometer stop value. Print it out, slap it on a clipboard, and stick it permanently in your car like I do. Record everything immediately, it should take seconds; you can add up the miles later. (Added: mileage log template for Excel)

What about driving from my self-employed home office to my day job with another employer? Nope, although it would be sweet to deduct such commuting costs, this is not qualified business travel. However, if you have a second site for your own business like a storefront, travel to/from your home office to/from that site can be deductible.

What if my UPS mailbox is next to my day job? Here’s where things get a bit fuzzy. You definitely aren’t allowed to deduct personal trips. But let’s say the supermarket is right next to your business bank. Since you’re already there, isn’t doing some grocery shopping the the eco-friendly thing to do? From my non-official understanding, you would need to prove that your trip to the bank is necessary and the primary reason for the trip, and not just an excuse to go to the supermarket. Making an actual deposit transaction would seem to be sufficient in that regard.

But if you are trying to say that your “business bank” is 30 miles away from your home office and just happens to be the one next door to your 9-5 job, then that may be much harder to justify. It is truly necessary to use that branch?

There’s more… You may also be able deduct mileage driven for charity, medical treatment, job searches, and moving.

References: IRS Publications 535, 463, and 529