You already know the basics: use it or lose it, the $680 carryover limit, grace period versus rollover toggle. Everyone talks about that stuff. What nobody talks about is how FSA rollover rules quietly break your benefits technology behind the scenes.
Payroll reconciliation, COBRA administration, HIPAA special enrollment, dependent care confusion, and ERISA audit trails. All of them can fail in ways that leave you scrambling for spreadsheets and sending apology emails. Here are the five edge cases that separate a solid platform from a mess.
1. The Payroll Deduction Echo
An employee elects $3,000 for the new year but carries over $400 from last year. Their effective balance is $3,400. Payroll deductions still run off $3,000. Most systems handle this by spreading deductions across fewer pay periods. Fine. But what about a mid-year qualifying event? The system must subtract the rollover amount from the remaining balance before applying the new election.
Cheap platforms just recalculate deductions without draining the rollover ghost. The result: the employee gets shorted at claim time. Demand that your system treat rollover as a separate, first-in-first-out layer, independent of the current-year election. If it can't, you'll chase reconciliation errors until the plan year ends.
2. The COBRA Nightmare
COBRA for FSAs sounds simple: the former employee pays the full cost of coverage to keep access. But rollover money from a prior year carries no COBRA premium. The employee already paid for that money through last year's salary reductions, so charging a premium on it again means paying twice. Only the current-year election carries a premium. Now picture a terminated employee with $200 in rollover and $1,000 in current-year funds. Two numbers. One system.
Many TPAs automatically deactivate the rollover bucket during COBRA, assuming all prior money is gone. That's wrong. The rollover should stay active but never contribute to COBRA premium calculations. A system that charges premium on the carryover is billing the former employee twice for money they already contributed.
3. HIPAA Special Enrollment Blind Spot
Under HIPAA, employees losing other coverage can enroll in your group health plan, including an FSA, outside open enrollment. That election is new money. It cannot include a prior-year rollover balance. Yet many systems let an employee with a carryover increase their election during special enrollment, effectively using the rollover to cover the new contribution.
IRS Notice 2013-71, which created the carryover option, treats the rollover as a separate balance available in addition to the current-year election. A special-enrollment election is new salary reduction for the current year, and the rollover cannot be folded into it. If your system doesn't keep the rollover separate during special enrollment, you're approving elections that don't match the plan document, and the correction lands on the employer.
4. The Dependent Care FSA Confusion
Most articles lump health FSAs and dependent care FSAs together. They shouldn't. Dependent care FSAs have no rollover option, except for a temporary exception under the Consolidated Appropriations Act, 2021, which let employers carry over unused amounts from the 2020 and 2021 plan years. Some employers use a 2.5-month grace period instead, which looks like a rollover but isn't.
During that grace period, the employee is also contributing to the new plan year, so the system must track two distinct balances: grace-period money and current-year money, with different claim deadlines. Most platforms treat them as one bucket, causing rejected claims for expenses incurred after the grace period ends.
5. The ERISA Audit Trail Gap
ERISA requires plan documents to specify rollover or grace period. That's easy. The hard part is accounting for forfeited amounts when employees leave mid-year. Rollover balances that go unused at termination are forfeited, and the employer may apply the forfeiture to a short list of permitted uses. Many systems don't track which forfeitures came from rollover versus current-year contributions.
Under IRS rules, a health FSA forfeiture may pay reasonable plan administration expenses, reduce the following year's salary reductions, or be returned to employees, each on a reasonable and uniform basis. The DOL treats salary reduction amounts as plan assets, so forfeiture accounting is a fiduciary responsibility. A rollover forfeiture is prior-year employee money, and a system that can't say which forfeitures came from a carryover can't support that accounting. Mixing the two sources produces a reconciliation that doesn't tie out, which is what a DOL audit flags.
What to Do Next
FSA rollover rules are a landmine, and most teams treat them as a footnote. Start with these steps:
- Audit your payroll deduction logic for mid-year changes when a rollover balance exists.
- Confirm your COBRA administrator charges no premium on rollover funds.
- Build a system rule that keeps rollover balances separate from mid-year election changes.
- Run a quarterly reconciliation report that separates rollover vs. current-year claims and forfeitures.
- Check whether a general-purpose FSA carryover is disqualifying employees from HSA contributions for the following plan year.
Next time a vendor says their system handles rollovers, ask them to walk through these five scenarios. If they hesitate, you know the code has cracks. This is the stuff nobody puts in the RFP.