Per diem and DRG
42 CFR 412.2 [1]
- Prospective payment per discharge is payment in full for inpatient operating costs, routine and ancillary included
- An hourly ER unit inside an admission raises the bill, not what the payer owes
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Case study · Hospital ED charge-integrity diagnostic
Hospital ED charge integrity: the hourly ER code that added 20 percent of gross and no cash
Short answer: ER visits held flat at 1,663 to 1,691 a month while one revenue-code 450 line began counting a unit for every hour of an inpatient stay. Gross rose 19 to 23 percent, the payers owed nothing more, and every percentage-based KPI fell while cash per visit rose.
Rev code 450 · 1.5 to 89 units per account
42 CFR 412.2 · payment in full per discharge
r = 0.894 · units vs length of stay
Diagnostic · found, not yet collected
Archetype
Hospital ED
Focus
Charge integrity
Metric
Units per account
Codes
Rev code 450
Horizon
Feb to Sep 2026
Length
6 min read
4.0to 104.2
ER charge units per inpatient account, before and after the hourly charge rule
1,663to 1,691
ER visits per month across the same period: flat
19to 23%
Added to monthly gross charges on flat volume, $9.14M in September
0.894r
Correlation between the hourly ER units and inpatient length of stay
ASP-RCM engagement records
Cash rising, headline KPI falling, both true
Rural acute-care district hospital, about 80 percent government payers, roughly $240M a year in gross charges; full revenue cycle with us since August 2025. A percentage can only fall while cash rises if the denominator grows faster.
Gross collection rate, February to September 2026
February 2026
12.41%baseline, 100%
September 2026
7.63%-38.5% vs February
BeforeAfter
Inpatient cash per visit, same months
February 2026
$5,991baseline, 100%
September 2026
$6,576+9.8% vs February
BeforeAfter
Visits flat, one line up 59-fold
Per inpatient account: ER visits versus ER charge units
One revenue-code 450 line moved from 1.5 to 89 units, one per hour of the admitted stay.
ER visits per monthlowest to highest month
1,663 to 1,691+1.7%: flat
Hourly ER line, units per inpatient accountrevenue code 450
1.5 before1.4% of after
after the rule
89 after59x, one per hour of stay
All ER charge units per inpatient accountevery ER line
4.0 before3.8% of after
after the rule
104.2 after26x
VisitsUnits beforeUnits after
Takeaway
Visits flat, one revenue-code line up 59-fold per inpatient account, and the extra units tracked length of stay at r = 0.894. That is a charge rule, not a clinical change.
Before and after, measure by measure
| Measure | Before | After | Read |
|---|---|---|---|
| ER visits per month | 1,663 | 1,691 | Flat |
| Units on the hourly ER line, per inpatient account | 1.5 | 89 | One per hour of stay |
| All ER charge units per inpatient account | 4.0 | 104.2 | 26x |
| Units vs inpatient length of stay | r = 0.894 | Tracks the stay, not the visit | |
| Added to monthly gross charges | 19 to 23% | $9.14M in September | |
| Separately payable under per diem or DRG | No | Zero cash behind the units |
ASP-RCM engagement records
Payment in full per discharge, so the units bought nothing
Denials that were not denials
$14K to $132K, then $1.5M to $2.4M a month
- 97 percent were line write-offs on claims the payer had already paid
- 92 percent sat on ER or inpatient accounts; 88 percent were Medicaid
One $165,921 line
Military health plan inpatient account
- That payer pays the ER portion of an admission on a separate outpatient claim
- Not a loss; the real cash behind it was a few hundred dollars
Five steps from charge build to a false KPI
1 · Charge buildHourly unit added
Revenue code 450 posts one unit per hour of stay.
2 · ClaimGross inflates
89 ER units per inpatient claim; gross up 19 to 23 percent.
3 · PaymentPayer pays the DRG or per diem
Payment in full under 42 CFR 412.2.
4 · PostingUnits adjusted off, labeled denial
Unpaid line on a paid claim, written off as a denial.
5 · ReportYield down, denials up
Yield 12.41 to 7.63 percent; denial write-offs ten to twenty times higher.
ASP-RCM operating method
Reporting integrity, rebuilt in the hospital's own numbers
- 1
Rebuilt yield by setting
- Inpatient, outpatient and ER cash per visit, separately
- One setting's charge build cannot move the headline
- 2
Separated payer denials from line write-offs
- A denial means a payer decision on an unpaid claim
- Adjustments on paid claims are contractual and reported as such
- 3
Put a gate on large single-line adjustments
- Unusual lines reviewed against the payer's rule before write-off or labeling
- 4
Traced the rule to its source
- Units per account by revenue code and month, with the length-of-stay correlation, handed to the charge-master owner
- 5
Reported cash first
- Cash per visit by setting and payer leads the monthly pack
- Percentages follow with their denominators shown
- 6
Left the charge decision with the hospital
- We documented the effect; the rule change is theirs to make
Like-for-like collection results: the companion hospital case study.
Status at October 27, 2026
- 0No cash outcome to claimThere was never cash behind the hourly units, so there is nothing to collect. This is a diagnostic and a reporting fix, not a recovery.
- ?The charge ruleWhether the hourly ER line stays in the charge build is the hospital's decision and had not been made at publication.
- WIPThe Medicaid write-off classificationLine write-offs on paid Medicaid claims are being re-labeled as contractual; the restated denial series is not yet complete.
- KPIGross collection rate as a KPIThe hospital still reports it. We report it with the denominator change disclosed until a replacement headline is agreed.
Frequently asked questions
What is an hourly ER charge and why did it produce no cash?
One ER revenue-code 450 line began posting one unit for every hour an admitted patient spent in the hospital, moving from 1.5 to 89 units per inpatient account. Inpatient stays are paid per discharge or per diem: under 42 CFR 412.2 the Medicare prospective payment is payment in full for inpatient operating costs, so the extra units raised gross charges without changing what any payer owed.
Does this mean the hospital's collections fell?
No: inpatient cash per visit rose from $5,991 to $6,576 over the same months. What fell was the gross collection rate, from 12.41 percent to 7.63 percent, because the denominator grew by 19 to 23 percent while cash did not.
Why did denial write-offs appear to jump?
Denial write-offs moved from $14K to $132K a month to $1.5M to $2.4M a month, but 97 percent of that was line-level write-offs on claims the payer had already paid: the hourly units adjusted off paid claims and labeled as denials. 92 percent sat on ER or inpatient accounts and 88 percent were Medicaid.
Is there a cash outcome from fixing this?
Not one that can be measured as collections, because there was never cash behind the units. The outcome is reporting integrity: yield by setting, cash per visit, and a denial figure that counts payer decisions only.
- 42 CFR 412.2: Basis of payment, inpatient prospective payment per discharge (govinfo)
- CMS Medicare Claims Processing Manual, Pub. 100-04 (Chapter 3 Inpatient Hospital Billing; Chapter 4 Part B Hospital)
- National Uniform Billing Committee: UB-04 data set and official code file
Checked October 27, 2026. Rules change; confirm against the source before relying on them. Client figures are archetype aggregates from ASP-RCM engagement records; no client is named.
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