Basic Deduction Ability

• Technically, yes, you can deduct charges associated with a residential phone for work. This applies to both landlines and cellphones. However, the phone cannot be your primary line.
  
  

The Catch

• The IRS considers your first residential line -- that is, your primary line -- to be personal. You cannot deduct charges for work on a primary line for this reason. This is true even if you use the phone for business purposes. However, you can deduct work-related charges on nonprimary lines. This means that to deduct phone expenses related to work, you have to have a separate landline or cellphone you use for business purposes. You can't prorate the cost of the phone.
  
  The IRS states the regulation about residential phones as follows on their website, IRS.gov: "You cannot deduct any charge ... for basic local telephone service for the first telephone line to your residence, even if it is used in a trade or business."
  
  

The Reimbursement Issue

• Typically, you cannot deduct any work-related charge for which your employer reimburses you. This rule applies to the residential phone you use for work. If your employer pays the bill for basic services and other charges like long distance, he -- not you -- notes the costs as a business expense.
  
  

Proof of Business Use

• To deduct work-related charges on a residential line, you must have evidence showing the phone is used for business. Ideally, this means your business phone has a separate phone number than your primary phone, and you keep your phone billing statements that show the numbers called. Because billing statements often show only the number, duration of the call and the region to which the call was made, it is to your benefit to keep a spreadsheet of all the numbers you call throughout the year. Identify which number belongs to which business or business associate on the spreadsheet. This way, you can look at your bill and separate nonbusiness and business calls as needed, and you can prove your deduction amount is valid in an audit. If you use your nonprimary line for both business and nonbusiness calls, figure out what percentage of calls are for business and deduct only that amount.