J.K. Lasser's Your Income Tax 2013: For Preparing Your 2012 Tax Return

19.14 Telephone Costs

For business calls made outside of your employer’s office or at home, keep a record or diary of business calls to support your deduction. To avoid the problem of allocating the costs of a single phone for both business and personal use, consider a separate phone for business use only.

- - - - - - - - - -

Caution

Deducting Telephone Costs

To support your deduction, keep a record of business calls made at home or anywhere outside your employer’s office.

- - - - - - - - - -

Deduction barred for basic charge of first phone line.

You may not claim as a deductible home office expense any part of the standard monthly charge for the first telephone line into your home. This disallowance rule only applies to the first telephone line. If you have more than one telephone line and use additional lines in a home office, costs for these lines remain deductible, subject to restrictions (19.13). The restriction does not affect deductibility of long-distance calls, phone rentals, or optional services such as call waiting, call forwarding, three-way calling, or extra directory listings.