CKD HCC Coding: N18.9 Has No V28 HCC

Quick Answer

N18.9 is a billable ICD-10-CM code. Under CMS-HCC V28 for payment year 2026 it has no payment HCC. N18.1 and N18.2 are the same valid-no-mapping result. N18.30 and N18.31 map to HCC 329. N18.32 maps to HCC 328. N18.4 maps to HCC 327. N18.5 and N18.6 map to HCC 326.

If the note supports a stage and the assigned code is unspecified, that is a documentation and query problem, not a missing map. Do not promote N18.9 to N18.31 from a lab row.

*Release: FY2026 ICD-10-CM period 2, April 1, 2026 through September 30, 2026. CMS-HCC V28, payment year 2026, is at full weight for non-PACE organizations. Community Non-Dual Aged (CNA) coefficients are shown only where the current CMS source files support them. Interaction terms are applied only inside the RAF tool, so this article does not publish a standalone interaction coefficient.*

At a glance

Checked N18, N17, and related codes. FY2026 period 2 identity plus CMS-HCC V28 mapping:

N18, N17, I12, and I13 exist in the FY2026 order file as non-billable headings. Code to a billable child.

HCC 329 is labeled "Chronic Kidney Disease, Moderate (Stage 3, Except 3B)." HCC 328 is "Chronic Kidney Disease, Moderate (Stage 3B)." HCC 327 is "Chronic Kidney Disease, Severe (Stage 4)." HCC 326 is "Chronic Kidney Disease, Stage 5." Those labels and the CNA values above come from the CMS V28 PY2026 relative-factor file. Other enrollment segments use different coefficients in that same file. Do not treat 0.127, 0.514, or 0.815 as a universal RAF.

Stage 3 and worse is the V28 payment set

The V28 payment map follows the ICD-10-CM code, not the word "CKD."

Checked stage 3 unspecified and stage 3a codes (N18.30, N18.31) map to HCC 329. The checked stage 3b code (N18.32) maps to HCC 328. Stage 4 (N18.4) maps to HCC 327. Stage 5 (N18.5) and ESRD (N18.6) map to HCC 326.

Official Guidelines Section I.C.14.a.1 classify CKD by severity. Stage 2, N18.2, is mild CKD. Stage 3, N18.30 through N18.32, is moderate CKD. Stage 4, N18.4, is severe CKD. N18.6 is assigned when the provider has documented end-stage renal disease. If both a CKD stage and ESRD are documented, assign N18.6 only.

N18.1, N18.2, N18.9, and N19 are not "unknown." They are verified valid-no-mapping rows under V28. N18.9 is the usual miss because it is billable, it looks complete, and it still contributes nothing to a V28 CMS-HCC score.

Unspecified is allowed. It is also a dead V28 map.

FY2026 Official Guidelines Section I.A.9.b say unspecified codes are for use when the record is insufficient to assign a more specific code. Section I.B.18 adds that unspecified codes should be reported when they most accurately reflect what is known for that encounter, and that it is inappropriate to select a more specific code the record does not support.

That is why N18.9 remains the correct ICD-10-CM answer when the stage was never documented. It is still verified no-HCC-mapping under V28. The coding question and the risk-adjustment question are not the same question.

N19, unspecified kidney failure, is also billable and verified no-HCC-mapping. It is not a quieter N18.9 and it is not a path to HCC 326.

HCC 328 and HCC 329 carry the same CNA

N18.32 maps to HCC 328. N18.30 and N18.31 map to HCC 329. The official V28 hierarchy file places HCC 328 above HCC 329. If a chart supports both a 3b code and a 3a or stage-3-unspecified code, HCC 329 does not also pay.

The official PY2026 COMMUNITY_NA coefficients for HCC 328 and HCC 329 are each 0.127. Applying that hierarchy does not change the stage-3 coefficient. Code the 3a versus 3b character the record supports because the code has to be correct. Do not recode N18.31 to N18.32 to "pick up" a heavier CKD weight. That heavier stage-3 weight is not in the PY2026 CNA column.

HCC 327 (0.514 CNA) and HCC 326 (0.815 CNA) sit above both of those categories. HCC 326 supersedes HCC 327, HCC 328, and HCC 329. HCC 327 supersedes HCC 328 and HCC 329. That is a hierarchy fact from the registered CMS file, not a sequencing preference.

N18.5 and N18.6 are not interchangeable

N18.5 is chronic kidney disease, stage 5. N18.6 is end stage renal disease. Both map to HCC 326, and both carry 0.815 CNA. The RAF line is the same. The code is still wrong if the documentation is wrong.

The Tabular inclusion term on N18.6 is "Chronic kidney disease requiring chronic dialysis." N18.5 has an Excludes1 note for chronic kidney disease, stage 5 requiring chronic dialysis (N18.6). Official Guidelines Section I.A.12.a define Excludes1 as a pure excludes note: "NOT CODED HERE!"

N18.6 also has a Tabular Use Additional note to identify dialysis status with Z99.2. Z99.2 is billable and verified no-HCC-mapping. Assigning it does not create a second CKD payment HCC. Skipping it when N18.6 is assigned is incomplete ICD-10-CM coding, not a way to change HCC 326.

Do not assign N18.6 from the word "kidney failure" alone. Official Guidelines Section I.C.14.a.1 require documented ESRD for N18.6.

Hypertensive CKD is I12 or I13. I12.9 does not map.

I10 is billable and verified no-HCC-mapping. Official Guidelines Section I.C.9.a.2 say to assign a code from category I12 when both hypertension and a condition classifiable to N18 are present, unless the provider indicates the CKD is not related to the hypertension. The appropriate N18 code is used as a secondary code to identify the stage.

That guideline is about the combination code, not about a CKD payment HCC on I12.9. I12.9 is billable and verified no-HCC-mapping. The V28 CKD payment HCC, when it exists, still comes from a mapped N18 stage code (or from a checked combination that itself maps, such as I12.0).

Checked I12 and I13 V28 results:

I12 and I13 are non-billable headings. A checked I50.9, heart failure unspecified, maps to HCC 226 with 0.360 CNA. This article does not inventory the I50 tree. Look up the documented heart-failure code.

I12 Excludes2 names acute kidney failure (N17.-). Acute kidney failure is not coded from the hypertensive CKD combination.

E11.22 does not replace the N18 stage code

E11.22 maps to HCC 37. The CNA coefficient in the MCP receipt is 0.166. The Tabular Use Additional note says to identify the stage of chronic kidney disease with N18.1-N18.6. N18 Code first names diabetic chronic kidney disease (E08.22, E09.22, E10.22, E11.22, E13.22) and hypertensive chronic kidney disease (I12.-, I13.-).

A checked stage-4 code, N18.4, maps to HCC 327. The CNA coefficient is 0.514. N18.9 remains verified no-HCC-mapping. Assigning E11.22 without the stage code is incomplete ICD-10-CM coding. It is not a way to pick up HCC 327, 328, 329, or 326 from the diabetes line.

Official Guidelines Section I.A.15 say the word "with" or "in" means "associated with" or "due to" when it appears in a code title, the Alphabetic Index, or a Tabular instructional note. The classification presumes that link unless the documentation clearly states the conditions are unrelated, or another guideline requires an explicit documented linkage. That is why diabetic CKD is coded as related when the Index or Tabular links them with "with." If the note says the CKD is from hypertension only, do not force E11.22.

See the diabetes HCC coding guide.

Z94.0 does not map. CKD after transplant still needs a stage.

Z94.0 is billable and verified no-HCC-mapping. N18 Use Additional names kidney transplant status (Z94.0) when applicable.

Official Guidelines Section I.C.14.a.2 say patients who have undergone kidney transplant may still have some form of CKD because the transplant may not fully restore kidney function. The presence of CKD alone does not constitute a transplant complication. Assign the appropriate N18 stage code and Z94.0. If a transplant complication such as failure or rejection is documented, see Section I.C.19.g. If the documentation is unclear, query.

This article does not inventory T86.1-. Look up the documented transplant-complication code.

Acute kidney failure is a checked valid-no-mapping family

N17 is a non-billable heading. Checked billable codes N17.0, N17.1, N17.2, and N17.9 are verified no-HCC-mapping under V28.

Acute kidney failure and chronic kidney disease are different categories. Do not lean on an N17 code expecting it to risk-adjust under this V28 receipt set. If both AKI and CKD are documented, code both as the record supports. I12 already Excludes2 N17.-.

Historical V24 reference

The current CMS 2026 Final ICD-10-CM Mappings file contains the generic CMS-HCC V28 column. It does not contain a generic CMS-HCC V24 column. HCC Buddy uses the CMS 2025 Midyear/Final ICD-10-CM Mappings file for its historical CMS-HCC V24, payment year 2025 reference. It does not infer a V24 mapping for FY2026 codes that are absent from that historical file.

The V28 map above applies to CY2026 non-PACE payment. Use the official mapping and model for the payment year and program under review. PACE uses a CY2026 blend and cannot be represented by one V28 or V24 mapping and coefficient.

This article does not publish a V24 coefficient in this section, and it does not turn a missing historical row into "no HCC."

Documentation and the query trigger

Official Guidelines Section I.B.2 require diagnosis codes at the highest number of characters available and at the highest specificity documented in the record. The provider, not the coder, establishes the diagnosis. A joint effort between provider and coder is required to get the documentation complete enough to code (guidelines introduction and Section I.B.18).

Official Guidelines Section I.A.19 add that code assignment is based on the provider's diagnostic statement that the condition exists, not on the clinical criteria the provider used to establish it.

What that means on a CKD chart:

Query when the record is internally inconsistent or incomplete, not to harvest a coefficient. HCC Buddy educational query language, not a CMS form:

"The assessment lists CKD with current treatment. Please document the current CKD stage (1, 2, 3a, 3b, 4, or 5) or whether this is ESRD, and whether the kidney disease is related to diabetes, hypertension, or another documented cause."

If the provider cannot specify a stage, keep N18.9. That is the guideline-compliant answer. It is also a V28 valid-no-mapping result. See provider query templates.

Primary sources

Disclaimer

HCC Buddy is not affiliated with, endorsed by, or approved by CMS, CDC, NCHS, AHA, AHIMA, or WHO. This page is original HCC Buddy education for risk-adjustment coders. It does not replace the official classification, the Official Guidelines, payer policy, or coder judgment. Every mapping and coefficient above is scoped to FY2026 period 2 and CMS-HCC V28 payment year 2026 CNA unless a different source is named. Re-check the official file for the date of service in front of you. HCC Buddy does not store PHI.

Written by the HCC Buddy Coding Team.

Frequently Asked Questions

Does N18.9 map to an HCC under V28?

No. N18.9 is billable, and the FY2026 period 2 MCP receipt plus the official 2026 Final ICD-10-CM Mappings file both return no CMS-HCC V28 category. The mapping status is verified no-HCC-mapping, not an incomplete file. N18.1, N18.2, and N19 have the same V28 result.

Which CKD codes map to HCC 328 or HCC 329?

N18.30 and N18.31 map to HCC 329. N18.32 maps to HCC 328. The official V28 labels are "Chronic Kidney Disease, Moderate (Stage 3, Except 3B)" and "Chronic Kidney Disease, Moderate (Stage 3B)." Both carry 0.127 CNA in the PY2026 V28 factor file. Other segments differ. HCC 328 supersedes HCC 329.

Do N18.5 and N18.6 map to the same HCC?

Yes. Both map to HCC 326, Chronic Kidney Disease, Stage 5. The CNA coefficient is 0.815. N18.6 is the ESRD code and is assigned when the provider documents ESRD. If both a stage and ESRD are documented, Official Guidelines Section I.C.14.a.1 assign N18.6 only. N18.5 Excludes1 names stage 5 requiring chronic dialysis (N18.6).

Does I12.9 map to a CKD HCC?

No. I12.9 is billable and verified no-HCC-mapping under V28. Official Guidelines Section I.C.9.a.2 still require the I12 combination when hypertension and N18 CKD are both present unless the provider says they are unrelated. The mapped N18 stage code is what can create the CKD payment HCC. I12.0, the stage 5 or ESRD hypertensive combination, maps to HCC 326.

Does E11.22 capture the CKD HCC by itself?

No. E11.22 maps to HCC 37 with 0.166 CNA. The Tabular Use Additional note still wants N18.1-N18.6. Official Guidelines Section I.A.15 treat the word with or in as associated with or due to unless the documentation clearly states the conditions are unrelated. A checked N18.4 maps to a separate CKD HCC.