If my cell phone is part of a shared expense how much of my portion can I deduct?

[twasz18]

I am one of three people paying the bill and my device is used for business and personal use.

[Hal_Al · Accepted solution]

None.

The costs of a cell phone  may be a business expense, but only the additional costs in using a cell phone for business are deductible. If you pay a flat rate on a phone used for business and personal calls, the tax court has held that the flat rate is for your personal phone and you incurred no additional charges for business use. You have no deduction. (TC Memo 2007-151).