Hey friends, last month, Biscuit the corgi went in for his annual checkup. He walked out paying nothing, the way his plan's preventive coverage is built to work. Three weeks later, a bill landed in his mailbox for $1,037. Same blood, same lab, same doctor. The only thing that changed between the visit BHC covered in full and the visit that cost him a month's rent was one letter on a piece of paperwork nobody told Biscuit existed. If you have ever opened a surprise medical bill and thought "how is this even possible," this issue is for you. About 154 million Americans are on employer-sponsored health insurance right now. The average family plan runs $26,993 a year all-in, most of it paid by the employer, which is more than most households pay for housing. And most of us couldn't explain, on the spot, what we are actually buying for that kind of money. Today we fix that. By the end of this email you will know exactly how a $0 visit turns into a $1,037 bill, and the one question to ask at your next appointment so it doesn't happen to you - Shivang
Scope note
This is a 101 issue, which means it is the simplified version. I am focusing on commercial employer-sponsored insurance (the most common kind), and skipping the deep complexity of Medicare, Medicaid, the VA, TRICARE, the Indian Health Service, CHIP, short-term plans, and the dozen flavors of supplemental coverage. Each of those gets its own future issue. If anything in here feels incomplete, that is on purpose. Your specific plan, state, and situation may differ from Biscuit's, and I will say that out loud throughout. None of this is medical, legal, or financial advice. It is education to help you ask better questions
A quick recap from the last letter (medical billing 101): Biscuit is the corgi who twisted his ankle on a Tuesday and learned how a $20,000 emergency room charge turns into a $2,400 patient bill. He is back this week, and his story has a twist. His annual checkup last month came out to $0, the way Affordable Care Act (ACA) preventive coverage is supposed to work. Then a piece of follow-up testing that came out of that checkup that was billed for $1,037.
Welcome back to American health insurance.
To make sense of how a $0 visit produced a $1,037 follow-up bill, you need a quick tour of what insurance is, where it came from, who's involved, and what kind of plan Biscuit is on. We'll do all of that and then come back to the bill.
Biscuit walked out of his annual paying nothing. Then his follow-up cost him $1,037. How?
What is insurance, and how did the US version end up this strange?
That year the federal government froze wages to keep wartime inflation from spiraling, which meant employers were legally barred from giving raises even though they were desperate to attract workers from a labor pool that was mostly off fighting in the war. The War Labor Board ruled that fringe benefits, including health insurance, didn't count as wages and were therefore exempt from the freeze.
Companies started offering insurance in place of raises. Workers loved it. Employers loved it more because it was cheaper than a real raise. A year later the IRS made it tax-free for both sides, which is roughly the policy equivalent of pouring kerosene on a small campfire. Blue Cross enrollment more than tripled between 1940 and 1945, from 6 million Americans to 19 million.
The wage freeze ended in 1945. The benefit did not. Eighty years later your health insurance is still stapled to your job, which means if you switch jobs you switch insurance, and if you lose your job you can lose your insurance too. This setup is normal almost nowhere else on the planet.
The non-profit Blues did not see the next chapter coming. For-profit insurance companies showed up, cherry-picked the healthy young office workers, charged them less than the Blues had to, and left the Blues stuck with the expensive patients. By the 1990s most Blue Cross plans had quietly converted to for-profit themselves rather than die out. Today most US insurers are publicly traded companies, which means their profit grows when premiums grow, and premiums grow when costs grow, and costs grow when you, um, continue to exist.
The government still plays three major roles in whatever is left of this. It runs insurance directly for people over 65 (Medicare) and people with low incomes (Medicaid). It subsidizes plans for people without job-based coverage through the ACA marketplace. And it sets the rules every other private insurer has to follow, including the one that says most plans have to cover certain preventive services without any out-of-pocket cost. That rule is Section 2713 of the Affordable Care Act (the 2010 law sometimes called Obamacare, which from here on we'll just call the ACA).
A few other government programs I am skipping here: the VA for military veterans, TRICARE for active-duty families, the Indian Health Service for Native Americans, and CHIP for kids whose families earn slightly too much for Medicaid. Each covers millions of people and works very differently from anything in this issue.
The preventive-coverage rule is not as simple as "preventive care is free." For the zero-cost coverage to actually apply, three things have to be true at once:
The service has to be on the official preventive list (KFF maintains a public tracker of all of them).
The provider has to be in-network.
Preventive care has to be the main reason for the visit.
Some plans are exempt from the rule entirely: older "grandfathered" plans (set up before the ACA passed in 2010), short-term plans, and faith-based health-sharing ministries. HealthCare.gov itself notes the caveat upfront on its preventive care page: "$0 cost isn't guaranteed in all cases."
Hold onto all of that. The not-as-simple-as-it-sounds part is going to matter in about three minutes.
Biscuit, in case you forgot, works at Barkingham Bakery. The bakery picked his plan. His insurer is BHC, the same one we met in the last letter.
The four players, and where your money actually goes
Every doctor visit you have ever had, and every one you will ever have, involves four players. They all want different things from the same encounter, which is most of why this whole experience feels so weird from the inside. (Real US healthcare has more players than four, including pharmacy benefit managers, brokers, and claims administrators. Four is what you need to read your bill.)
1. You. You pay the premium every month whether you are sick or not. You pay the deductible (the amount you have to spend on care before insurance starts pitching in) before anything else kicks in. You pay copays and coinsurance on top of all that. In our story, Biscuit pays $150 a month out of his paycheck.
2. Your employer (or the ACA marketplace). Picks the plan and usually covers most of the premium. You pick from whatever menu they hand you. Barkingham Bakery pays $650 a month toward Biscuit's plan, which is roughly the national average for single coverage in 2025 ($657 a month, per KFF).
3. The insurer. Collects the premiums, decides what is covered, negotiates rates with doctors. In our story, BHC.
4. The provider. The doctor and the hospital. Delivers care, sends the bill. In our story, Dr. Singh (Biscuit's primary care doctor) and Barkingham General.
The quick math on Biscuit: his $150 plus the bakery's $650 lands at $800 a month, or $9,600 a year, all going to BHC before anyone has so much as a sniffle. That is the price of the seat at the table, and it gets paid whether Biscuit sees a doctor that year or not. The national average for single coverage in 2025 is $9,325 a year (KFF), so Biscuit's plan sits slightly above average, which tracks because he is on a PPO.
Before any of those 154 million Americans see a doctor, they need to know what kind of plan they are actually on. The plan type controls almost every dollar that follows. That’s what we are going into next!
The five plan types you'll actually meet
There are hundreds of plan names out there, and they all sound like they were generated by a CVS receipt printer ("BluePlus Advantage Premier HSA 2500" and friends). Underneath all that branding, almost every plan is one of five types. The first three are the main characters. The last two are hybrids.
HMO (Health Maintenance Organization). Cheap premiums, narrow doctor network. The reason HMOs cost less is that the insurance company saves money by tightly controlling where you go for care, and passes some of those savings on to you. You have to get a "referral" from your primary care doctor before you can see a specialist. If Biscuit had been on an HMO, Dr. Singh would have had to write him a referral before he could see the ankle specialist.
PPO (Preferred Provider Organization). Higher premiums, much wider network, no referrals needed. PPOs prioritize choice: you can usually keep your existing doctor and skip the bureaucracy of asking for permission to see specialists. Biscuit has one, which is why he could walk straight into the ankle specialist last year.
HDHP (High Deductible Health Plan). Cheap premium, but a big deductible (usually $3,000 to $8,000) you pay yourself before insurance kicks in. These plans bet that you stay healthy this year; if you don't, your premium savings vanish at the first big bill. Often paired with a tax-free Health Savings Account for medical expenses. If Biscuit had an HDHP, last year's ankle X-ray would have come straight out of his pocket until he hit that deductible.
POS (Point of Service). A hybrid of HMO and PPO. It is the compromise pick: cheaper than a PPO if you stay in-network, more flexible than an HMO if you ever need to step outside. You pick a primary care doctor like an HMO, but you can also go out-of-network at higher cost like a PPO. Biscuit on a POS would have needed Dr. Singh's referral, or paid more to skip it.
EPO (Exclusive Provider Organization). Strictest of the network plans. Think of it as a PPO with a hard wall: easy access inside the network, no help if you step outside. No referrals required, but go out-of-network and your insurance pays nothing (except for true emergencies). Biscuit on an EPO who accidentally saw an out-of-network specialist would have owed the full chargemaster bill.
Here's the part you should actually be mad about.
Between 2024 and 2025, HDHPs went from 27% of US workers to 33% (KFF, 2025). That's millions of people moved onto a plan where the first $3,000 to $8,000 of any medical bill is theirs to cover before insurance pays a cent. Most of them didn't choose it. Their employer did, and most of them won't find out what that means until something goes wrong.
The honest trade behind every plan
Every one of those five plans is the same trade in different clothes. You can pay more every month in premium, or you can pay more when you actually get sick, in deductibles and out-of-pocket costs. No plan lets you pay less of both. That plan doesn't exist, whatever your HR rep implies at open enrollment.
Pick the low premium and you carry more risk the day something goes wrong. Pick the low deductible and you pay for that cushion every month whether you use it or not. At open enrollment you're choosing which kind of bill you'd rather be holding when the year is over.
Biscuit is on a PPO. His deductible this year is $1,800, right around the 2025 national average for single coverage of $1,886 (KFF). The morning he walked into Dr. Singh's office for his checkup, he hadn't spent a dollar against it.
How doctors and insurers actually work together
Medical billing 101 covered most of the bill mechanics, so here is the short version.
In-network doctors like Dr. Singh signed a contract with BHC that gives BHC a discount on every service in exchange for being on BHC's preferred-provider list. That discounted price is called the "negotiated rate." Every service Dr. Singh provides has a numeric code attached, and the code decides how much BHC actually pays. The annual wellness checkup code (officially CPT code 99396) is one of dozens of codes the ACA designates as preventive, which means BHC has to cover it without charging Biscuit anything (since Biscuit's plan meets all the conditions).
For the longer version of how the bill, the EOB, and the negotiated rate fit together, go back to issue 2. For now, the only piece that matters is this: Biscuit's annual visit was billed under code 99396, BHC covered it in full under ACA preventive rules, and Biscuit walked out of the office paying nothing.
Then his test results came back.
❝ A clean screening usually costs you nothing. A screening that finds something usually costs you the follow-up.
Why Biscuit's follow-up cost $1,037
Quick reconnect. Biscuit went in for his annual physical and walked out having paid nothing. A week later his cholesterol came back a little high, so Dr. Singh ordered a few follow-up tests. Three weeks after that, a bill landed in his mailbox for $1,037.
Nobody did anything wrong here. Dr. Singh ordered sensible tests. Biscuit showed up for them. BHC processed the claim correctly. So where did the bill come from?
One word: timing.
Insurance treats your care differently depending on when it happens. Care that happens before anything is wrong is called preventive. Your annual physical, a routine cholesterol check, the standard once-a-year screening. When the conditions from Section 1 are met (the service is on the official list, the provider is in-network, the plan is not exempt), the ACA can require your plan to cover preventive care at no cost to you.
Care that happens after something turns up is called diagnostic. The follow-up test, the second look, the "let's check that again." Diagnostic care does not get that protection. It goes through your deductible like any other bill.
The strange part is that the same test can be either one. A cholesterol test on a healthy patient is preventive. The identical test, run again because the first result was high, is diagnostic. The test did not change. The reason for the test changed, and the reason is what insurance charges for.
That is the whole story behind Biscuit's bill.
His annual physical and his first cholesterol screening counted as preventive, and his plan met all the conditions, so BHC covered them in full. Biscuit paid $0.
His follow-up tests counted as diagnostic. The repeat cholesterol panel, the glucose test, and the EKG were ordered because the screening had flagged something, which makes them a workup for a known concern. BHC put the full amount toward Biscuit's deductible. He had not met that deductible yet, so all $1,037 was his to pay.
CMS spells this out in its own guidance: a health plan may charge you for care that results from a preventive service, even when the preventive service itself was covered at no cost (CMS, ACA Implementation FAQs Part 12). A covered checkup that leads to a billed follow-up is the system working as designed.
Your health insurance was invented as a workaround to a wartime wage freeze, locked in by a 1943 IRS ruling, and quietly turned for-profit somewhere between Reagan and Clinton without anyone really voting on it. Your employer picks the plan, your insurer picks your doctor, and the bill is the math at the end. The math has rules. Knowing them is the only part of this that was ever optional.
What to do this week (callout)
If you're a patient, three things you can do to understand your coverage better:
Before any annual or screening, ask the front desk one question: "if my results come back with something that needs follow-up, how is the follow-up billed?" The answer is almost always "diagnostic, runs through your deductible." Knowing in advance lets you plan for it instead of being surprised by it. This is information you have a right to.
When the EOB arrives in your mail, read every code. Look at which charges were processed as preventive (covered at zero / lower cost if the conditions are met) versus diagnostic (applied to your deductible). If a charge looks wrong, you have the right to request an itemized bill, ask your provider to verify the codes, and appeal. KFF's most recent analysis of ACA Marketplace plans found that roughly 34% of appealed denials were overturned on internal appeal in 2024 (KFF, 2026 brief on 2024 data). That number applies only to Marketplace plans, only to denials (not to deductible charges like Biscuit's), and only to appeals that actually got filed. Fewer than 1% of denied claims are ever appealed. The takeaway is not that appeals are a magic button. It is that they exist, they sometimes work, and most people never try.
Know your deductible status going into any follow-up visit. If you are going to owe out of pocket anyway, ask your doctor whether other care you have been postponing (a procedure, a specialist visit, a needed test) can be done while you are already paying. Once you cross your deductible, your insurer starts covering a much larger share of the bill for the rest of the plan year.
If you're a clinician, two moves for your patients:
When you order a follow-up test, flag the billing context in real time: "this is going to be billed as diagnostic since we are looking into a finding, so it will probably go through your deductible. Here is why I am ordering it, and here is roughly what to expect." Patients almost never get this heads-up, and it is the difference between trust and a surprise bill.
Train your front desk to give patients a one-line explainer when they schedule the annual: "the annual visit itself is typically covered under your insurance's ACA preventive rules, but any follow-up testing afterward may be billed differently. Check with your insurer if you're not sure." Most patients have never been told this, and the front desk is the cheapest place to fix that.
Bonus resource for both groups:
Two links worth bookmarking before your next visit.
KFF's preventive services tracker lists every service designated as preventive under the ACA, sorted by category (cancer screenings, chronic-condition screenings, immunizations, sexual health, pregnancy-related, general health promotion). Whether your plan actually covers it at zero cost depends on the conditions we walked through earlier in this piece.
HealthCare.gov's preventive care page walks through those rules and conditions, including their own caveat printed right at the top: "$0 cost isn't guaranteed in all cases." Read both before scheduling anything you think should be free.
If you want the deeper version of any of this (the five plan types side-by-side, the full ACA preventive services list, what modifier 25 actually means in code), it is all in the Converus knowledge base.
Hit reply. I read everything, and the best questions become the next lesson — Shivang
Sources cited in this issue
KFF, 2025 Employer Health Benefits Survey. https://www.kff.org/health-costs/2025-employer-health-benefits-survey/ — used for: $26,993 average family premium total ($6,850 worker share, $20,143 employer share), $9,325 average single premium total, $657/month average employer single contribution, $1,886 average single deductible, 154M Americans on employer-sponsored coverage, plan-type enrollment (46% PPO, 33% HDHP, 12% HMO, 9% POS).
CMS, ACA Implementation FAQs Set 12. https://www.cms.gov/cciio/resources/fact-sheets-and-faqs/aca_implementation_faqs12 — used for: the preventive-vs-diagnostic cost-sharing clarification (the modifier 25 trapdoor).
CMS, "Background: The Affordable Care Act's New Rules on Preventive Care." https://www.cms.gov/cciio/resources/fact-sheets-and-faqs/preventive-care-background — used for: Section 2713 of the ACA preventive services mandate.
AMA Journal of Ethics, "The US Health Care Non-System, 1908-2008." https://journalofethics.ama-assn.org/article/us-health-care-non-system-1908-2008/2008-05 — used for: 1929 Baylor schoolteachers at 50 cents/month for 21 days hospital care; the 1942 War Labor Board fringe-benefits ruling.
The Hill, "The employer-health insurance connection: an 'accident of history'" (2019). https://thehill.com/opinion/healthcare/469739-the-employer-health-insurance-connection-an-accident-of-history/ — used for: October 1942 Emergency Price Control Act wage-freeze authorization.
HealthCare.gov, "Preventive health services." https://www.healthcare.gov/coverage/preventive-care-benefits/ — used for: the explicit caveats on the ACA preventive rule, including "$0 cost isn't guaranteed in all cases," in-network requirement, and the three sets of preventive services.
KFF, ACA Preventive Services Tracker. https://www.kff.org/aca-preventive-services-tracker/ — used for: linked in body so readers can see every service that counts as preventive under the ACA, by category.
History.com, "How Health Insurance Got Its Start in America." https://www.history.com/articles/health-insurance-baylor-plan — used for: Blue Cross enrollment growth from 6M (1940) to 19M (1945), the for-profit takeover in the 1980s-90s.
KFF, "Claims Denials and Appeals in ACA Marketplace Plans in 2024" (March 2026). https://www.kff.org/patient-consumer-protections/claims-denials-and-appeals-in-aca-marketplace-plans-in-2024/ — used for: 34% of appealed claim denials overturned on internal appeal in 2024, <1% of denied claims ever appealed, scope caveat (Marketplace plans only).
