Medicare crossover claims: why the secondary never gets billed, and how to catch it
Stephen Grinich
HealthSpark CEO and Founder••10 min read
What is a Medicare crossover claim?
A crossover claim is a claim Medicare forwards to the patient's secondary insurance after Medicare pays its share, so the secondary can pick up the 20% coinsurance without you submitting anything. It only happens when the crossover is set up for that patient and that plan.
In our mobile and telehealth PT practice, about a third of our Medicare patients don't have it set up. For every one of them, the 20% is never billed unless we build the secondary claim ourselves.
- Accepting Medicare doesn't automatically mean the secondary pays the rest. It depends on each patient's coverage.
- Crossover only happens when it's set up. When it isn't, the secondary never gets the claim, and you won't see a denial.
- Medicare's payment notice tells you whether it forwarded the claim. Check it for every Medicare visit.
- When it wasn't forwarded, send the secondary claim yourself, with what Medicare paid.
The version of this that came up recently
A PT starting a mobile outpatient practice asked in a Facebook group for clinicians going out on their own:
"if you accept Medicare, does that automatically translate to a secondary Medicare coverage (eg UHC or BCBS), or how does it work if you accept Medicare but are OON for all other providers?"
Crossover usually gets described as automatic. That has not been our experience, and the gap between the two is where the 20% goes missing.
Does accepting Medicare mean the secondary pays the rest?
No. Medicare pays first and leaves 20% coinsurance behind. What happens to that 20% depends on what the patient carries behind Medicare, and on whether the secondary ever receives the claim.
| What the patient has behind Medicare | What it does with the 20% | What the patient may still owe |
|---|---|---|
| Medicare Supplement (Medigap) | Many plans pick up most or all of it | Little or nothing, depending on the plan letter |
| Secondary PPO (e.g. UHC or BCBS) | Processes it under the plan's own benefits | Some cost sharing is still possible |
| No secondary | Nothing | The full 20% |
Every row except the last assumes the secondary actually gets the claim. That is the part most practices never check. For the payment order itself, and why not being contracted with a supplement's carrier doesn't make the patient out-of-network, see Medicare secondary billing for PT/OT practices.
How Medicare crossover works
After Medicare pays its share, it can send the claim straight on to the patient's secondary insurance, along with what it paid. For that to happen, Medicare has to already know about the patient's secondary plan and have that plan set up to receive claims from it.
That setup exists patient by patient, plan by plan. Nothing about accepting Medicare sets it up for you, and nothing on the patient's cards tells you whether it's there.
Why the secondary never gets the claim
About a third of our patients don't have crossover set up, so the secondary plan never gets the claim from Medicare to cover the 20% coinsurance.
We didn't see denials in these cases, because the claim was simply never submitted to the secondary insurance plan. That is what makes this expensive. A denial lands in a report and someone works it. A claim that was never forwarded produces nothing to work: Medicare's payment posts, the visit looks mostly paid, and the remaining 20% balance just sits there.
On a $100 allowed visit, the missing secondary is $20. A patient on a twice-weekly plan of care for eight weeks is sixteen visits, or about $320 that no payer and no report will ever ask you about. Multiply that by a third of your Medicare caseload.
How to tell whether Medicare forwarded a claim
Look at Medicare's payment notice for the claim (billers call it the remittance). When Medicare forwards a claim, it adds a short note saying so: the claim was also sent to the patient's supplemental insurer. In billing software that note shows up as code MA18.
| On Medicare's payment notice | What it means | What to do |
|---|---|---|
| Note: forwarded to supplemental insurer | The secondary has the claim | Nothing. Watch for the secondary's payment. |
| No note | Nothing was sent to the secondary | Send the secondary claim yourself. |
The trap is that the second row looks exactly like a normal paid claim. Nobody notices a missing note by accident. Someone has to check for it on purpose, on every Medicare claim where the patient has a secondary.
How to collect the 20% when crossover doesn't happen
Medicare pays its portion, but the remaining 20% balance just sits there unless you create and submit the secondary claim yourself, with all the additional information about what Medicare paid you. Done by hand, that is four jobs per Medicare visit.
1. Verify Medicare and the secondary before every visit
Confirm that Original Medicare is still the primary and that the secondary on file is active. A secondary that lapsed or changed is the same dead end as a missing crossover, one step earlier. Checking only at intake misses plans that change mid-episode.
2. Check every Medicare payment for the forwarding note
When Medicare pays a visit for a patient with a secondary, look for the note that it was forwarded. No note means that visit needs a secondary claim, and the best time to send it is right away, while Medicare's payment is in front of you.
3. Send the secondary claim with what Medicare paid
The secondary doesn't re-review the visit. It pays based on what Medicare already decided, so the claim has to show that. Everything it needs is on Medicare's payment notice:
- What Medicare paid, for each service on the visit
- What Medicare adjusted off, and what it left for the patient
- The date Medicare paid
If you bill on paper, attaching Medicare's payment notice to the claim does the same job. Either way, the numbers have to match what Medicare actually paid.
4. Track the claim until the secondary pays
Submitting the secondary isn't the end of it. Keep every visit open until the remaining balance is paid by the secondary or moved to the patient, so a secondary claim that stalls doesn't turn into the same silent balance you just recovered.
How we handle it now
We don't outsource that work anymore. We set up an automation that verifies Medicare and secondary coverage before every visit and tracks whether Medicare forwarded each claim to the patient's secondary insurance on file. If Medicare didn't, it automatically creates the secondary claim using Medicare's payment details and submits it, so we get that 20%.
This all runs in the background now. We get a timeline for each claim and every remaining payment, so we can see exactly where everything sits in the queue.
- Sep 3Coverage verified: Medicare Part B + BCBSSep 3 · Before visitBefore visit
- Sep 4Claim sent to MedicareSep 4 · $100.00$100.00
- Sep 18Medicare paidSep 18 · $80.00$80.00
- Sep 18Medicare didn't forward it to BCBSSep 18 · FlaggedFlagged
- Sep 18Secondary claim built and sent to BCBSSep 18 · $20.00$20.00
Our AI verifies Medicare and secondary coverage before every visit, reads each Medicare payment for whether the claim was forwarded to the secondary on file, and when it wasn't, creates the secondary claim from Medicare's payment details and submits it. Every claim gets a timeline showing each payment still outstanding, so you can see exactly where the 20% sits.
Frequently asked questions about Medicare crossover
Does Medicare automatically bill secondary insurance?
How do I know if Medicare forwarded a claim to the secondary?
Why didn't the secondary insurance deny the claim?
Should I also send the claim to the secondary if Medicare forwarded it?
Does a Medicare Supplement always pay the full 20%?
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