Included in the reported 564 total suggested amendments to the legislation were proposals to increase or remove the originally planned $2,000 contribution cap, exclude FSAs from the excise tax on high cost health insurance plans and clarify the reimbursement role of FSAs for over-the-counter medications. Save Flexible Spending Plans is considering the amendments filed by eight senators "on both sides of the aisle" that call for (at the least) increasing the cap on FSA contributions a "step in the right direction."

"Without a higher cap, Congress could force plan participants, including many fighting chronic illnesses, to forgo necessary medical treatment, prescriptions and supplies for financial reasons, resulting in a deterioration of health and an increase in hospitalizations and overall health care system costs," said Jackson.

Those threatened by a change to the structure of FSAs include the benefit companies that manage FSAs for employers, employers that offer FSAs to their employees and the millions of plan participants who have come to rely on the benefit to budget and pay for eligible out-of-pocket health care costs, says Jody Dietel, spokesperson for Save Flexible Spending Plans.

But some argue the extent to which the $2,500 cap on FSA contributions would actually have on employees. Only about 20 percent of workers offered an FSA take advantage of it, Paul Fronstin, director of the health research and education program at the Employee Benefits Research Institute told USA Today. And the use-it-or-lose-it rule, which forces participants to decide how much will be needed to set aside in pretax money from their paychecks, is a discouragement to participants who argue the difficulty in predicting health expenses.

The most recent estimate of the average contribution to an FSA is about $1,400, Fronstin said. "So the average person wouldn't be affected" by the $2,500 limit.