In general, once the usage of the phone becomes primarily for business purposes. For example, if you are requiring an employee to carry the phone at all times a

In general, once the usage of the phone becomes primarily for business purposes. For example, if you are requiring an employee to carry the phone at all times and to answer it after hours and deal with clients, it is a business usage and should be paid for by the company. However, that does not mean that the entire service should be reimbursed as many people now have family plans and paying the entire service would unfairly burden the company as well. Additionally, technically if they did reimburse the entire bill, you likely would owe taxes on the non-business reimbursement as it is "income". One other point, if the business is requiring 100% cell phone access, in many states an employee may have a claim to additional pay, even if salaried. If the company is asking you to provide them your cell number for on-call times only and for notification of an issue when you are already being compensated for on-call time then likely it is more gray and not a "requirement" to reimburse you. However, I have seen most companies still do something in these cases. Generally in a startup though, you are not there because you are worried about getting the $50-$100 monthly reimbursement because startups are generally focused on results not building up the enterprise systems to track this type of stuff (until they mature more). To my point, you are generally investing your time beyond 8 hrs a day, and are likely not taking a market level salary in lieu of options so it would seem the cell phone is a minor thing in the end. Just my opinion though.