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How do I Keep Log for Auto Expenses?

How Do I? ... Keep a log for automobile expenses

If you use your car for business purposes, you may have learned that keeping track and properly logging the variety of expenses you incur for tax purposes is not always easy. Practically speaking, how often and how you choose to track expenses associated with the business use of your car depends on your personality; whether you are a meticulous note-taker or you simply abhor recordkeeping. However, by taking a few minutes each day in your car to log your expenses, you may be able to write-off a larger percentage of your business-related automobile costs.

Regardless of the type of record keeper you consider yourself to be, there are numerous ways to simplify the burden of logging your automobile expenses for tax purposes. This article explains the types of expenses you need to track and the methods you can use to properly and accurately track your car expenses, thereby maximizing your deduction and saving taxes.

Expense methods

The two general methods allowed by the IRS to calculate expenses associated with the business use of a car include the standard mileage rate method or the actual expense method. The standard mileage rate for 2007 is 48.5 cents per mile. In addition, you can deduct parking expenses and tolls paid for business. Personal property taxes are also deductible, either as a personal or a business expense. While you are not required to substantiate expense amounts under the standard mileage rate method, you must still substantiate the amount, time, place and business purpose of the travel.

The actual expense method requires the tracking of all your vehicle-related expenses. Actual car expenses that may be deducted under this method include: oil, gas, depreciation, principal lease payments (but not interest), tolls, parking fees, garage rent, registration fees, licenses, insurance, maintenance and repairs, supplies and equipment, and tires. These are the operating costs that the IRS permits you to write-off. In general, the actual expense method usually results in a greater deduction amount than the standard mileage rate. However, this must be balanced against the increased substantiation burden associated with tracking actual expenses. If you qualify for both methods, estimate your deductions under each to determine which method provides you with a larger deduction.

Substantiation requirements

Taxpayers who deduct automobile expenses associated with the business use of their car should keep an account book, diary, statement of expenses, or similar record. This is not only recommended by the IRS, but essential to accurate expense tracking. Moreover, if you use your car for both business and personal errands, allocations must be made between the personal and business use of the automobile. In general, adequate substantiation for deduction purposes requires that you record the following:

  • The amount of the expense;
  • The amount of use (i.e. the number of miles driven for business purposes);
  • The date of the expenditure or use; and
  • The business purpose of the expenditure or use.

Suggested recordkeeping: Actual expense method

An expense log is a necessity for taxpayers who choose to use the actual expense method for deducting their car expenses. First and foremost, always keep your receipts, copies of cancelled checks and bills paid. Maintaining receipts, bills paid and copies of cancelled checks is imperative (even receipts from toll booths). These receipts and documents show the date and amount of the purchase and can support your expenditures if the IRS comes knocking. Moreover, if you fail to log these expenses on the day you incurred them, you can look back at the receipt for all the essentials (i.e. time, date, and amount of the expense).

Types of Logs. Where you decide to record your expenses depends in large part on your personal preferences. While an expense log is a necessity, there are a variety of options available to track your car expenditures - from a simple notebook, expense log or diary for those less technologically inclined (and which can be easily stored in your glove compartment) - to the use of a handheld device, palm pilot or software. Software programs specifically designed to help track your car expenses can be easily downloaded onto your blackberry or palm pilot.

Timeliness. Although maintaining a daily log of your expenses is ideal - since it cuts down on the time you may later have to spend sorting through your receipts and organizing your expenses - this may not always be the case for many taxpayers. According to the IRS, however, you do not need to record your expenses on the very day they are incurred. If you maintain a log on a weekly basis and it accounts for your use of the automobile and expenses during the week, the log is considered a timely-kept record. Moreover, the IRS also allows taxpayers to maintain records of expenses for only a portion of the tax year, and then use those records to substantiate expenses for the entire year if he or she can show that the records are representative of the entire year. This is referred to as the sampling method of substantiation. For example, if you keep a record of your expenses over a 90-day period, this is considered an adequate representation of the entire year.

Suggested Recordkeeping: Standard mileage rate method

If you loathe recordkeeping and cannot see yourself adequately maintaining records and tracking your expenses (even on a weekly basis), strongly consider using the standard mileage rate method. To claim the standard mileage rate, appropriate records would include a daily log showing miles traveled, destination and business purpose. If you incur mileage on one day that includes both personal and business, allocate the miles between the two uses. A mileage record log, whether recorded in a notebook, log or handheld device, is a necessity if you choose to use the standard mileage rate.

If you have any questions about how to properly track your automobile expenses for tax purposes, please call our office. We would be happy to explain your responsibilities and the tax consequences and benefits of adequately logging your car expenses.


If and only to the extent that this publication contains contributions from tax professionals who are subject to the rules of professional conduct set forth in Circular 230, as promulgated by the United States Department of the Treasury, the publisher, on behalf of those contributors, hereby states that any U.S. federal tax advice that is contained in such contributions was not intended or written to be used by any taxpayer for the purpose of avoiding penalties that may be imposed on the taxpayer by the Internal Revenue Service, and it cannot be used by any taxpayer for such purpose.