Aggregate stop-loss insurance caps the total amount a self-funded employer pays in medical claims during a single plan year. The employer funds its own health plan and pays claims out of its own assets; the aggregate stop-loss carrier reimburses whatever the group’s combined claims run above a pre-set ceiling, usually 120% or 125% of what the plan was expected to spend. It is a backstop against a bad claims year across the whole workforce, not a safety net for any one person’s medical bill.
What Aggregate Coverage Protects Against
Self-funded employers typically carry two stop-loss policies that address different risks. Specific stop-loss covers a single person whose claims exceed an individual threshold during the plan year. Aggregate stop-loss covers the group as a whole: it responds when flu seasons, surgeries, maternity cases, and chronic conditions all stack up and push total spending beyond the budget, even if no one employee ever hit the specific threshold.
This is the boundary that catches employers off guard. If one employee generates $800,000 in cancer treatment costs and no one else has an unusual year, aggregate stop-loss likely pays nothing, because that claim is handled under the specific policy. Aggregate exists for the opposite pattern: dozens of moderately expensive claims that together outrun expectations.
Employees never deal with the stop-loss carrier directly. Their claims go through a Third Party Administrator and are paid from the plan’s funds. The stop-loss policy sits one layer above, protecting the employer’s balance sheet rather than paying any provider.
How the Attachment Point Is Set
The aggregate attachment point is the dollar figure where the carrier’s obligation begins. Underwriters set it as a percentage above the group’s expected annual claims, and that percentage is the corridor the employer absorbs before reimbursement starts. The most common corridor is 125% of expected claims. 120% is also widely used, and some groups negotiate as tight as 110% or as wide as 150%.1American Academy of Actuaries. Academy Stop Loss Comments 06 29 2012 A tighter corridor means the carrier starts paying sooner, so premiums rise accordingly.
The math starts with an aggregate factor, which is the expected monthly claims cost per covered employee. Say the factor is $400 per employee per month and the employer has 500 covered employees. Expected monthly claims come to $200,000. Over twelve months that is $2,400,000 in expected annual claims. At a 125% corridor, the aggregate attachment point lands at $3,000,000. The employer pays every dollar of claims up to that figure; the carrier reimburses anything above.
Monthly Census Adjustments
The attachment point is not fixed on day one. Headcount shifts throughout the year as people are hired, terminated, or move on and off the plan, so the carrier recalculates monthly. Each month, the aggregate factor is multiplied by the actual number of covered lives that month. The twelve monthly figures are then added together at year-end to produce the final annual attachment point. The threshold stays proportional to actual exposure rather than frozen to a January headcount.
Regulatory Floors on the Attachment Point
Carriers and state regulators impose a floor that the aggregate attachment point cannot drop below, no matter what the corridor math produces. The NAIC Stop Loss Insurance Model Act, which many states have adopted in some form, sets the minimum aggregate attachment point for groups of 50 or fewer at the greater of $4,000 per group member, 120% of expected claims, or $20,000. For groups of 51 or more, the floor is 110% of expected claims.2National Association of Insurance Commissioners. Stop Loss Insurance Model Act The floors stop stop-loss policies from functioning as thinly disguised traditional insurance.
State rules vary. California has historically set aggregate floors at the greater of $5,000 per person, 120% of expected claims, or $40,000, and the District of Columbia applies similarly elevated thresholds for groups of 100 or fewer. The Department of Labor has taken the position that states may regulate stop-loss policies issued to plan sponsors, including setting minimum attachment points, because those laws regulate the insurance company rather than the ERISA plan itself.3U.S. Department of Labor. Technical Release No. 2014-01 Confirm your state’s minimums before assuming you can negotiate a tight corridor.
What the Carrier Wants Before Quoting
Quoting aggregate stop-loss is an actuarial exercise, and underwriters cannot build an accurate projection from a headcount alone. Carriers typically ask for a group census with birth dates, genders, and zip codes for everyone covered, because regional healthcare costs vary sharply. They want at least 24 months of paid claims history showing utilization trends and seasonal patterns. They want the Summary Plan Description to understand covered services, exclusions, and plan limits. And they require disclosure of any known high-cost claimants, meaning employees already undergoing expensive treatment or diagnosed with conditions likely to produce large claims in the coming year.
Lasering
After reviewing the data, a carrier may “laser” specific individuals. Lasering is an underwriting move where the carrier either excludes a high-risk person from stop-loss coverage or sets a significantly higher specific deductible for that person. If an employee had a $500,000 transplant last year with ongoing costs expected, the carrier might laser that individual at $300,000 instead of the $150,000 that applies to everyone else. Lasering keeps the overall premium competitive while isolating the known risk. Employers unhappy with aggressive lasers sometimes shop competing carriers or accept a higher aggregate premium in exchange for a no-laser contract.
Contract Windows and Run-Out
Aggregate contracts run on a 12-month plan year, but they include a run-out period that accounts for the lag between when a service is rendered and when the claim is actually paid. The two most common formats are named for their incurred and paid windows.
- A 12/15 contract covers claims incurred during the 12-month plan year and paid within 15 months of the plan year’s start. That is a 3-month run-out.
- A 12/18 contract uses the same incurred window but allows claims to be paid up to 18 months from the plan year’s start, giving a 6-month run-out.
A longer run-out captures more claims, which produces a more accurate final aggregate total. The trade-off is that the employer waits longer for reimbursement, because the carrier will not calculate the final attachment point until the run-out window closes.
Terminal Liability Coverage
If an employer moves from self-funded to fully insured coverage, a gap can open. Claims incurred under the self-funded plan may still be working their way through the TPA when the new fully insured policy takes effect, and the new insurer typically will not pay them. Terminal liability coverage extends the stop-loss contract’s paid window by an additional three or six months after cancellation, catching those stragglers. It has to be elected at the start of the contract and paid for across the full contract period. Waiting until cancellation is already in motion is too late.
Filing for Reimbursement
After the plan year and the run-out period both close, the employer compares total paid claims against the final calculated attachment point. If claims cleared the threshold, the employer submits a reimbursement package, usually through a carrier portal. The package includes a reconciliation report with monthly enrollment, monthly claims totals, the calculated attachment point for each month, and documentation that payments came from plan funds.
The carrier audits the submission to confirm every claim was eligible under the plan document and that the aggregate math is correct. Claims that should have been paid by another source, that fell outside the plan’s terms, or that already triggered specific stop-loss reimbursement may be stripped out of the aggregate calculation. The audit typically runs 30 to 60 days, longer for complex cases or incomplete files. Once it clears, the carrier issues payment to the employer. The structure is pure indemnity: the employer fronts the cash all year, then recovers after the fact.4Health Care Administrators Association. What is Stop Loss Insurance
Monthly Aggregate Accommodation
Waiting until after year-end can strain cash flow, especially for smaller groups where one bad month blows through reserves. Some carriers offer a monthly aggregate accommodation rider that provides interim reimbursement during the plan year. If cumulative paid claims at the end of any policy month exceed the cumulative attachment point by more than a set amount, often $1,000, the carrier advances the excess rather than making the employer wait. The rider is typically available for groups under 300 enrolled employees and must be elected at the start of the contract. It does not change the final year-end reconciliation; it simply moves money forward.
Aggregate Coverage Inside Level-Funded Plans
Level-funded plans blend self-funding mechanics with the predictability of traditional insurance. The employer pays a fixed monthly amount that bundles expected claims, administrative fees, and stop-loss premiums for both specific and aggregate exposure. If total claims come in under expectations, the employer may receive a surplus refund at year-end. If claims run over, the embedded aggregate coverage absorbs the excess.
The aggregate stop-loss built into a level-funded plan works the same way as a standalone policy. It sets an attachment point above expected claims and reimburses overruns. The difference is that the employer never shops the coverage separately or files for reimbursement directly; the level-funded carrier handles both pieces as part of the package. For smaller employers who want self-funding’s upside without the cash flow swings, this is usually how aggregate protection reaches them.