My small business s-corp provides 24x7x365 on-call IT services. Right now my business is just me -- single-owner s-corp with no other employees -- but in theory, all future employees would be required to have a cell phone for after-hours on-call support. Historically I have maintained two cell phone lines -- 1 personal, 1 business... but I am looking to reduce expenses and I want to drop the second line. If my accountable reimbursement plan clearly documents the requirement for a cell phone so clients can reach me after hours 100% of the time, can I justify reimbursing 100% of my cell phone expense from the s-corp? It seems to me in that scenario that: * Any personal use should be considered incidental and negligible, since the business requires the cell phone even outside of normal business hours; and * The total expense to the business is the same: either the business pays 100% for a second line which is business-use-only; or 100% for a personal cell phone line that gets mixed use. Either way it costs the same amount for the business and does not change my taxable income. I have the exact same question for my home internet service. The same 24x7 on-call requirement demands that I maintain reliable high-speed internet access 100% of the time for after-hours utilization. Even if I NEVER use it for personal use, I would still have to have the service. My business address is my home address, and I maintain several servers in my home server-closet which host client websites and services -- so technically speaking, my home internet is used for business 100% of the time -- even if I'm away from my desk watching netflix.