How to Write Down My Gas Expense for My Income Tax

When gas prices increase, deducting actual expenses can save you money on your taxes.
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If you or your partner use your own vehicles to run nonreimbursed errands for your employer, going to the doctor or doing charity work, you can deduct the gas you buy for these trips from your income taxes. While many taxpayers take the standard mileage deduction allowed by the Internal Revenue Service, if you have a gas-guzzler, deducting your actual expenses can provide a larger deduction. Deducting your gas expenses requires meticulous records; you must be able to distinguish between the deductible gas you buy and the gas used on personal trips.

Step 1

Purchase two notebooks to keep in your car to record your gas purchases. At the top of the first page on one notebook, make columns and label them "Date," "Beginning Odometer Reading," "Ending Odometer Reading," "Gallons Purchased," "Price per Gallon," "Total Purchase Price," "Total Miles," "Average MPG," "Deductible Miles" and "Deductible Expense." Write "Gas" on the front cover of the notebook.

Step 2

Write "Miles" on the front cover of the second notebook. Make columns on the first page labeled "Date," "Deductible Miles Driven" and "Reasons for Trip."

Step 3

Fill your car with gas and write down the date, beginning odometer reading, gallons purchased, price per gallon and total purchase price in the "Gas" notebook. For example, write "10/10/15," "26,382," "12.083," "$3.369," and "$43.97." You cannot fill out the other columns until you buy more gas and have entries in your "Miles" notebook.

Step 4

Complete the information for the "Miles" notebook by entering the date, number of deductible miles and reason for the miles anytime you make a deductible trip. For example, if you go to the office supply store for your employer, write "10/12/15," "42 miles" and "Supply run for boss."

Step 5

Enter information into your "Gas" notebook each time you buy gas. Subtract your beginning odometer reading from your ending odometer reading to calculate your total miles between purchases. Divide your answer by the number of gallons purchased to determine your average miles per gallon (MPG). For example, if you drove 187 miles between purchases and bought 13.485 gallons of gas, your average MPG is 13.87.

Step 6

Add together any deductible miles in your "Miles" notebook that you drove between gas purchases and write the amount in the "Deductible Miles" column in your "Gas" notebook.

Step 7

Divide your deductible miles by your average MPG and multiply by the price per gallon to calculate your deductible expense. For example, 42 miles divided by 13.87 MPG equals 3.028 gallons. 3.028 gallons times $3.369 per gallon means your deductible gas expense is $10.20. Write the answer in your "Gas" notebook and staple the gas receipt to the page.

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