Adopt and document an accepted allocation basis, such as square footage for office space, children in care, and like the cell phone example, number of units to be allocated.
It is important that the basis used is documented so it can provide justification to auditors and the readers of the financial statements.
Identify the expenses that are directly allocated to one of the functional categories, or that need to be allocated amongst several categories using an indirect cost allocation.
Keep timesheets for all employees, if their responsibilities overlap different departments and programs.
Remain consistent with the functional and cost allocation basis. Review the allocation methodology on a periodic basis, and if necessary, make and document any necessary changes.
Use an accounting system that allows for the segregation of accounts by multiple segments to allow for proper allocation and generation of financial statements.