Deduct utility expenses only for your trade or business. Local telephone service. If you used your home phone for business, do not deduct the base rate (including taxes) of the first phone line into your residence. But you can deduct any additional costs you incurred for business that are more than the base rate of the first phone line.
For example, if you had a second line, you can deduct the business percentage of the charges for that line, including the base rate charges.