Carriers may charge employers a base annual servicing fee and a monthly fee per employee enrolled in a Medical and/or Dependent Care FSA.

Flexible spending account (FSA) plans are administered by the benefits carrier an employer chooses. Carriers usually charge employers a small fee per FSA participant for administration.
For example, below is an overview of employer FSA fees on Zenefits — an all-in-one HR, benefits, and payroll platform.
Zenefits FSA fees
Zenefits charges companies a base annual servicing fee of $150 for the plan year and a monthly fee per employee enrolled in a Medical and/or Dependent Care FSA. The 2 contract options are: Annual ($4/employee per month, prepaid for the year) or Month-to-Month ($5/employee per month, monthly payments). Companies who are currently enrolled in FSA will be able to choose either contract option upon renewal of their current plan.