Overview: The most calculation-intensive topic on the exam — this section works through the exact math of how patient and insurer responsibilities are computed, step by step, within a policy year.

Once a deductible is satisfied, cost-sharing shifts to coinsurance — a percentage split between insurer and insured. The most common split is 80/20: the insurer pays 80% of covered charges above the deductible; the insured pays 20%. The insured's 20% obligation continues until total out-of-pocket costs (deductible + coinsurance) reach the stop-loss limit, also called the out-of-pocket maximum. After that point, the insurer pays 100% of covered expenses for the remainder of the year.

The Three Phases of a Policy Year

Phase 1 — Deductible: Insured pays 100% of covered expenses until the deductible is met.

Phase 2 — Coinsurance: Insured pays 20% (in an 80/20 plan); insurer pays 80%. Both deductible payments and coinsurance payments count toward the stop-loss.

Phase 3 — Stop-loss reached: Insurer pays 100% of remaining covered expenses for the year.

Full Worked Example: $1,500 Deductible, 80/20 Coinsurance, $5,000 Stop-Loss

Assume all expenses are in-network and covered by the plan.

Event 1 (January): ER visit — $1,000 allowed charge

Deductible status: $0 of $1,500 met
Insured pays 100%: $1,000
Insurer pays: $0
Running totals: Deductible met = $1,000; OOP met = $1,000

Event 2 (March): MRI — $1,200 allowed charge

Remaining deductible: $500
Insured pays remaining deductible: $500 → deductible now fully satisfied
Remaining bill subject to coinsurance: $1,200 − $500 = $700
Insured's coinsurance (20% of $700): $140
Insurer's coinsurance (80% of $700): $560
Insured pays on this event: $500 + $140 = $640
Running totals: Deductible met = $1,500 (done); OOP met = $1,640

Event 3 (August): Outpatient surgery — $20,000 allowed charge

Deductible already satisfied
Full coinsurance: 20% of $20,000 = $4,000 — but check the stop-loss
OOP remaining before hitting $5,000 limit: $5,000 − $1,640 = $3,360
Insured pays: $3,360 (stop-loss kicks in; insured doesn't owe the full $4,000)
Insurer pays: $20,000 − $3,360 = $16,640
Running totals: OOP met = $5,000 (stop-loss reached)

Event 4 (November): Specialist visit — $200 allowed charge

Stop-loss already reached
Insured pays: $0
Insurer pays: $200

Event	Allowed Cost	Insured Pays	Insurer Pays	Cumulative OOP
ER visit	$1,000	$1,000	$0	$1,000
MRI	$1,200	$640	$560	$1,640
Surgery	$20,000	$3,360	$16,640	$5,000
Specialist	$200	$0	$200	$5,000
Totals	$22,400	$5,000	$17,400

Simpler Calculation: $2,000 Claim, $500 Deductible, 20% Coinsurance, $3,000 Stop-Loss

Patient pays deductible: $500 → $1,500 remains
Patient pays 20% coinsurance on $1,500: $300
Insurer pays 80% coinsurance on $1,500: $1,200
Patient total: $500 + $300 = $800
Insurer total: $1,200
Verify: $800 + $1,200 = $2,000 ✓
Stop-loss check: $800 < $3,000, so stop-loss does not apply here

FAQ

Q: Does the deductible count toward the stop-loss limit?
Yes. The stop-loss (out-of-pocket maximum) is the ceiling on total out-of-pocket spending — deductible payments and coinsurance payments both accumulate toward it. Once the combined total of all qualifying out-of-pocket payments reaches the stop-loss, the insurer takes over completely.

Q: What doesn't count toward the stop-loss?
Monthly premiums do not count. Expenses for services not covered by the policy do not count. Under many plans, out-of-network charges that exceed the plan's allowed amount also do not count. This means a patient can theoretically pay more than the stop-loss in a year if they use out-of-network providers.

Q: What is the difference between the stop-loss in the individual context versus the employer context?
For individual policyholders, the stop-loss is simply the out-of-pocket maximum in the policy — the point at which the insurer pays 100% for the rest of the year. For self-funded employers, "stop-loss" refers to a separate insurance policy the employer purchases to protect itself from catastrophically large aggregate claims. The exam primarily tests the individual policyholder meaning: the out-of-pocket maximum that protects consumers from unlimited cost-sharing exposure.