MS-DRG 999: Ungroupable
MS-DRG 999 is the inpatient billing code for ungroupable. It is one of 772 codes Medicare uses to classify a hospital stay by diagnosis, procedures and severity.
What this code actually classifies
| Official title | UNGROUPABLE |
|---|---|
| Code | MS-DRG 999 |
| Type | ** |
"With MCC" means a major complication or comorbidity was recorded; "with CC" a complication or comorbidity; "without CC/MCC" neither. These modifiers move a stay into a higher-paying group, which is exactly why it is worth checking that the complications on your bill match what actually happened during your stay.
Source: CMS FY 2026 IPPS Final Rule (CMS-1833-F), Table 5. MS-DRG definitions are published by CMS and are in the public domain.
How to use this when disputing your bill
- Check the code matches your stay. Ask for a fully itemized statement and confirm the diagnosis, the procedures and any recorded complications are things that actually happened.
- Question the modifiers. If your bill says "with MCC" but no major complication occurred, that single word may be worth thousands. Ask for a coding review against the medical record.
- Anchor your request in the paid figure, not the billed figure. "Federal Medicare data shows an average payment of a small fraction of the billed amount for MS-DRG 999" is a concrete, verifiable benchmark a billing office can act on.
- Ask about financial assistance separately. A coding dispute and a financial assistance application are different requests, and you can make both. Look up what your hospital is required to offer.
Frequently asked questions
What does MS-DRG 999 mean on my hospital bill?
It means the hospital classified your inpatient stay as "Ungroupable". MS-DRGs group a stay by diagnosis, the procedures performed and the severity of your condition, and the group determines what Medicare pays.
Can I dispute a bill with this code?
Yes. Ask in writing for a fully itemized statement, check that the diagnosis and procedures actually match your stay, and if the code seems more intensive than the care you received, ask for a coding review against your medical record. Miscoding is a common and legitimate ground for a bill to be reopened.