The FY2027 ICD-10-CM code set took effect October 1, 2026. It adds 190 billable diagnosis codes, makes 30 FY2026 codes non-billable, and revises 4 descriptions. Most changes demand more specific documentation: laterality, anatomic site, disease subtype, exact BMI, named substance, exposure type or pregnancy location.
The additions are not the urgent part. The 30 codes that changed status are. A code your providers selected on September 30 may no longer be a valid billable selection on October 1.
This guide covers ICD-10-CM diagnosis codes only. ICD-10-PCS procedure codes changed separately and are not covered here.
What is the FY2027 ICD-10-CM update?
ICD-10-CM is the diagnosis code set used across all U.S. healthcare settings. The CDC's National Center for Health Statistics (NCHS) maintains ICD-10-CM. CMS distributes the files, maintains ICD-10-PCS, and publishes the Official Guidelines jointly with NCHS.
The main ICD-10-CM release takes effect October 1. Additional codes may be implemented on April 1 when a midyear update is issued. Both happen. NCHS implemented 42 new diagnosis codes for health-related social needs effective April 1, 2023, and CMS published a full set of April 2026 ICD-10-CM files. Some April releases add codes; others, such as April 1, 2024, correct typographical errors only.
The October 1, 2026 release is the code set in use for FY2027. Treat an April 1, 2027 update as possible rather than ruled out, and check the CMS ICD-10 files page and the NCHS ICD-10-CM files page before you assume the October set is the only one you need this year.
One label trips teams up every year. FY2027 codes take effect in October 2026, not October 2027. The October 2027 release will be FY2028, and it has not been published. Those files normally appear the preceding June.
FY2027 ICD-10-CM changes at a glance
| FY2027 change | Number | What it means |
|---|---|---|
| New classification entries | 238 | Every new row in the Tabular List, including non-billable categories |
| New billable diagnosis codes | 190 | Codes you can report on or after October 1, 2026 |
| Previously billable codes affected | 30 | 15 removed outright; 15 now non-billable parent codes |
| Rows removed from the classification | 21 | The 15 removed billable codes plus 6 non-billable headings |
| Existing descriptions revised | 4 | Same code numbers, updated wording |
| Total FY2027 billable ICD-10-CM codes | 74,879 | The active reportable code set |
All figures come from the CMS FY2027 ICD-10-CM Addendum and the CMS FY2027 Code Descriptions in Tabular Order .
Summaries conflate the 238 and the 190. The classification gained 238 rows. Of those, 190 are codes you can put on a claim. The other 48 are parent categories that organize the new children. Both numbers are correct, and they answer different questions.
Why "30 deleted ICD-10 codes" is the wrong description
FY2027 gets summarized as "190 added, 30 deleted." All 30 do stop working as billable selections, so the shorthand holds operationally. It covers two different events, and the difference changes how you fix your systems.
- 15 codes left the classification entirely. They are gone from the Tabular List. An updated encoder returns nothing for them.
- 15 codes remain in the Tabular List as non-billable parent codes. They still appear in lookups and still look familiar. They can no longer be reported, because more specific child codes now sit underneath them.
That second group causes more field errors. A code that still returns a search result reads as valid to a provider picking from a favorites list.
Which 30 ICD-10-CM codes are no longer billable in FY2027?
Now non-billable parent codes (15): D69.1 · I42.0 · I42.8 · I49.8 · M72.2 · M86.8X1 · M86.8X2 · M86.8X3 · M86.8X4 · M86.8X5 · M86.8X6 · M86.8X7 · M86.8X8 · Z68.1 · Z87.890
Removed from the classification (15): S23.420A · S23.420D · S23.420S · T52.8X1A · T52.8X1D · T52.8X1S · T52.8X2A · T52.8X2D · T52.8X2S · T52.8X3A · T52.8X3D · T52.8X3S · T52.8X4A · T52.8X4D · T52.8X4S
Replacements for every family are in the before-and-after table below. Validate against the CMS FY2027 Addendum before changing a production system.
Will an FY2026 code cause a claim rejection after October 1, 2026?
For encounters and discharges on or after October 1, 2026, a code that is no longer valid as a billable ICD-10-CM selection can fail code-validity edits and may be rejected or returned for correction.
Where it fails varies by clearinghouse, payer and claim-processing workflow. Some edits catch it before submission; some payers return it. Calling every one an identical instant rejection overstates it.
The operational rule holds: an FY2026-only code should not reach an FY2027 claim.
Which ICD-10-CM chapters changed most in FY2027?
These counts are billable codes only, taken from the CMS FY2027 Addendum.
| ICD-10-CM area | New billable codes | Why coders should care |
|---|---|---|
| Injury, poisoning and other external causes (S-T) | 60 | Largest FY2027 expansion. The organic-solvent toxic-effect family was rebuilt around named substances |
| Pregnancy, childbirth and the puerperium (O) | 44 | 28 codes for vanishing twin syndrome; 16 add site and laterality to ectopic pregnancy |
| Musculoskeletal and connective tissue (M) | 31 | Osteomyelitis laterality drives 24. Plantar fasciitis gets its own family. VEXAS syndrome gets a code |
| Factors influencing health status (Z) | 16 | BMI splits, exposure history, personal-history detail. Small codes, very large encounter volumes |
| Circulatory (I) | 9 | Cardiomyopathy subtypes and named arrhythmias |
| Respiratory (J) | 6 | Odontogenic sinusitis by sinus; pulmonary mycetoma |
| Digestive (K) | 6 | Pelvic disease category, moderate hepatic fibrosis, intestinal failure-associated liver disease |
| Congenital and genetic (Q) | 6 | Lynch, BRCA1, BRCA2, Li-Fraumeni and Loeys-Dietz syndromes |
| Neoplasms (C) | 3 | Secondary malignancy of larynx, pharynx and oral cavity |
| Blood (D) | 2 | Glanzmann thrombasthenia split out |
| Endocrine (E) | 2 | Postprocedural and post-bariatric hypoglycemia |
| Genitourinary (N) | 2 | Postprocedural nipple ischemia and necrosis |
| Mental and behavioral (F) | 1 | Gender identity disorder, in remission |
| Skin (L) | 1 | Carbuncle of flank |
| Symptoms and abnormal findings (R) | 1 | Abnormal gadolinium level in blood |
The top four account for 151 of the 190 additions. The other 39 are spread across eleven chapters, and most FY2027 summaries skip them. They are covered in the "Other FY2027 additions" section below.
Top 10 FY2027 ICD-10-CM changes medical coders need to know
1. Thirty previously billable codes stopped working the way they did
Fifteen codes left the classification. Fifteen became parent codes that still appear in lookups and can no longer be reported.
Every one of them is represented by family in the before-and-after table below. Run those families against your last 12 months of claims before you read a single new code.
2. Organic solvent toxic effects were rebuilt around named substances
This is the largest FY2027 change by code count, and most summaries skip it.
The entire T52.8X- family, Toxic effect of other organic solvents, was removed across all four intents and all three encounter types. Twelve billable codes gone. Three families replace it:
- T52.81- Toxic effect of alkenes
- T52.82- Toxic effect of cycloparaffins
- T52.89- Toxic effect of other organic solvents
Each carries accidental, intentional self-harm, assault and undetermined intent, each with initial encounter, subsequent encounter and sequela. That is 36 new codes from one restructure.
Two more substances got the same treatment: T59.82- hexamethylene diisocyanate, an industrial isocyanate, and T65.85- medetomidine, a veterinary sedative now appearing as a fentanyl adulterant. Twelve codes each.
Toxicology, emergency departments and occupational health should treat this as their first FY2027 item. T52.8X- was a high-traffic residual code and it no longer exists.
3. Dilated cardiomyopathy now requires a subtype
I42.0 became a non-billable parent. FY2027 adds:
- I42.00 Dilated cardiomyopathy, unspecified
- I42.01 Familial-genetic dilated cardiomyopathy
- I42.09 Other dilated cardiomyopathy
I42.01 carries the clinical weight. If the cardiologist documented a familial or genetic etiology, FY2027 has a place to put it. If the note says dilated cardiomyopathy and nothing more, I42.00 is the correct answer.
4. Other cardiomyopathies split out arrhythmogenic cardiomyopathy
I42.8 also became a non-billable parent:
- I42.81 Arrhythmogenic cardiomyopathy
- I42.89 Other cardiomyopathies, not elsewhere classified
Arrhythmogenic cardiomyopathy spent years inside a residual code. Cardiology and electrophysiology coders should expect I42.81 to absorb a share of former I42.8 volume.
5. Brugada syndrome and ventricular bigeminy received their own codes
I49.8, Other specified cardiac arrhythmias, was a heavily used residual code in cardiology. It became a parent for FY2027:
- I49.81 Brugada syndrome
- I49.82 Ventricular bigeminy
- I49.89 Other specified cardiac arrhythmias, not elsewhere classified
FY2027 also adds I47.22 , catecholaminergic polymorphic ventricular tachycardia (CPVT), under a separate category.
This is the FY2027 pattern in one example. A broad "other specified" code that coders carried forward for a decade now has named children underneath it. If the documentation identifies the arrhythmia, the classification identifies it too.
6. Plantar fasciitis and plantar fascial fibromatosis are now two different families
Podiatry and orthopedics should read this one twice. The two conditions are easy to conflate, and FY2027 separated them.
Plantar fasciitis is new. It has never had a dedicated ICD-10-CM code. FY2027 creates the M67.A- family:
- M67.A01 Plantar fasciitis, right foot
- M67.A02 Plantar fasciitis, left foot
- M67.A09 Plantar fasciitis, unspecified foot
Plantar fascial fibromatosis (Ledderhose disease) gained laterality. M72.2 became a non-billable parent, with M72.20 unspecified foot, M72.21 right foot and M72.22 left foot.
Fasciitis is inflammatory heel pain. Fibromatosis is a nodular proliferative disorder of the plantar fascia. Teams that used M72.2 as a catch-all for heel pain have a cleanup job, and it should trigger a sweep of diagnosis favorites, superbills and provider preference lists across podiatry, orthopedics and ASC coding , where surgeons maintain those pick lists rather than coding.
7. Osteomyelitis laterality drives 24 of the 31 musculoskeletal additions
Eight codes in the M86.8X- other osteomyelitis family became non-billable parents.
Seven split by laterality. M86.8X1 through M86.8X7, covering shoulder, upper arm, forearm, hand, thigh, lower leg and ankle and foot, each gained right, left and unspecified children. Shoulder is the pattern for all seven: M86.8X1 becomes M86.8X11 right, M86.8X12 left, M86.8X19 unspecified.
One split by site instead. M86.8X8, other site, has no laterality option. It became M86.8X80 skull, M86.8X81 face and sinuses, and M86.8X89 other site. Skull osteomyelitis, including Pott's puffy tumor, now has a dedicated code.
M86.8X9, multiple sites, was not touched and remains billable.
8. Obstetrics gained 44 codes, and most are not ectopic pregnancy
The obstetric expansion gets described as an ectopic pregnancy update. It is mostly something else.
28 of the 44 cover continuing pregnancy after vanishing twin syndrome, in category O31.4-, built on trimester and then fetus identification. Vanishing twin syndrome is the loss or resorption of one embryo in a multiple gestation while the pregnancy continues.
The remaining 16 add site and laterality to ectopic pregnancy, in category O00-. Interstitial and cornual ectopic pregnancy each gained right, left and unspecified, with and without an intrauterine pregnancy. Cervical ectopic pregnancy received O00.41 and O00.42.
Flag one code with your MFM and OB providers: cesarean scar ectopic pregnancy now has O00.31 without intrauterine pregnancy and O00.32 with. It is clinically distinct, rising in incidence, and had no code of its own before October 1.
9. Z codes: exact BMI, exposure history and personal history
Sixteen new Z codes look minor and touch very large encounter volumes, which makes them the quietest risk in FY2027 for risk adjustment and CDI teams.
BMI. Z68.1, BMI 19.9 or less, adult, became a non-billable parent. The calculated value now decides the code: Z68.18 for BMI 18.4 or less, Z68.19 for 18.5 to 19.9. Z68.18 sits at or below the clinical underweight threshold; Z68.19 does not.
Exposure history. Seven new Z77 codes: Z77.013 gadolinium, Z77.32 burn pits in war theater, Z77.33 Agent Orange, and Z77.40 / Z77.41 / Z77.42 / Z77.49 for blast overpressure at unspecified, low, high and other levels. These matter to any organization touching VA or military health populations. FY2027 also adds R78.72, abnormal gadolinium level in blood.
Personal history. Z87.890 became a non-billable parent, replaced by Z87.8901 social, Z87.8902 medical, Z87.8903 surgical gender transition, Z87.8904 intersex surgery and Z87.8909 unspecified. FY2027 adds Z87.893 for gender detransition.
One more worth knowing: Z86.17 , personal history of Clostridioides difficile infection.
10. The sternoclavicular sprain change has no one-character replacement
Most annual update work follows one shape: old parent code out, new child code in. S23.420 breaks it.
S23.420A, S23.420D and S23.420S, sprain of the sternoclavicular joint, were removed from the classification. No same-family child code waits underneath.
The sternoclavicular joint already has a sprain family in Chapter 19 under S43.6-, carrying unspecified, right and left, each with initial encounter, subsequent encounter and sequela. Depending on what the provider documented, that is the likely destination. Select the FY2027 code from the current Index and Tabular List based on the documented injury, the side and the encounter type.
A conversion table tells you something changed. It does not read the operative note.
Other FY2027 ICD-10-CM additions most summaries miss
The top four chapters hold 151 of the 190 new codes. The other 39 are smaller families, and several land in high-volume specialties. These come from the CMS FY2027 Code Descriptions in Tabular Order .
| New code(s) | Description | Who should check |
|---|---|---|
| C78.31 · C78.32 · C79.83 | Secondary malignant neoplasm of larynx, pharynx, oral cavity | Oncology, head and neck, ENT |
| QA1.71 | Lynch syndrome | Oncology, GI, genetics |
| QA1.790 · QA1.791 | Familial cancer syndrome with pathogenic BRCA1 / BRCA2 mutation | Oncology, breast surgery, OB-GYN |
| QA1.792 · QA1.798 | Li Fraumeni syndrome; other inherited neoplasm predisposition syndrome of multiple systems | Oncology, genetics |
| Q87.A | Loeys-Dietz syndrome | Cardiology, vascular, genetics |
| M04.3 | VEXAS syndrome | Rheumatology, hematology |
| E89.830 · E89.838 | Post bariatric hypoglycemia; other postprocedural hypoglycemia | Bariatric surgery, endocrinology |
| K6A.01 · K6A.09 · K6A.8 | Prevesical abscess; other pelvic abscess; other diseases of the pelvis, NEC | General surgery, urology, interventional radiology |
| K74.0A | Hepatic fibrosis, moderate fibrosis | Hepatology, GI |
| K76.83 | Intestinal failure-associated liver disease | GI, pediatrics, nutrition support |
| K31.B | Hypertrophic pyloric stenosis, in childhood | Pediatrics, pediatric surgery |
| J4B | Pulmonary mycetoma | Pulmonology, infectious disease |
| N99.860 · N99.861 | Intraoperative and postprocedural nipple ischemia; nipple necrosis | Plastic surgery, breast surgery, ASC coding |
| F64.A | Gender identity disorder, in remission | Behavioral health, primary care |
Three of these change how a chart gets read, not just which code gets picked.
Genetic cancer syndromes now have their own chapter range. The new QA1 category sits in Chapter 17, which the FY2027 Official Guidelines now title Q00-QA1. A documented Lynch syndrome or pathogenic BRCA1 or BRCA2 mutation is now a specific diagnosis code, not only a genetic-susceptibility status code. The documentation has to name the syndrome or the mutation.
Postprocedural hypoglycemia is now a complication code. E89.830 separates hypoglycemia after bariatric surgery from other postprocedural hypoglycemia. As with any complication of care, the provider must document the link between the procedure and the condition.
Breast surgery complications gained site detail. N99.860 and N99.861 identify nipple ischemia and nipple necrosis as intraoperative or postprocedural complications. Plastic and breast surgery coders working in ASCs should add both to their pick lists.
FY2027 before and after: which FY2026 codes changed and what to use instead
These twelve rows cover all 30 affected codes by family, plus the one brand-new family. If your team understands this table, the rest of FY2027 is lookup work.
| FY2026 code | FY2027 impact | New option or action | Documentation to check |
|---|---|---|---|
| D69.1 | Non-billable parent | D69.11 / D69.19 | Glanzmann thrombasthenia vs other qualitative platelet defect |
| I42.0 | Non-billable parent | I42.00 / I42.01 / I42.09 | Familial or genetic etiology |
| I42.8 | Non-billable parent | I42.81 / I42.89 | Whether the cardiomyopathy is arrhythmogenic |
| I49.8 | Non-billable parent | I49.81 / I49.82 / I49.89 | Named arrhythmia: Brugada, ventricular bigeminy |
| M72.2 | Non-billable parent | M72.20 / M72.21 / M72.22 | Which foot. Confirm fibromatosis, not fasciitis |
| (no code existed) | New family | M67.A01 / M67.A02 / M67.A09 | Plantar fasciitis diagnosis and which foot |
| M86.8X1 to M86.8X7 | Non-billable parents | Right / left / unspecified children | Site and side |
| M86.8X8 | Non-billable parent | M86.8X80 / M86.8X81 / M86.8X89 | Skull, face and sinuses, or other site. No laterality here |
| Z68.1 | Non-billable parent | Z68.18 / Z68.19 | Exact calculated adult BMI |
| Z87.890 | Non-billable parent | Z87.8901 to Z87.8909 | Type of transition documented |
| T52.8X1 to T52.8X4 (A/D/S) | Removed | T52.81- / T52.82- / T52.89- | Named solvent, intent, encounter type |
| S23.420A / D / S | Removed | Re-index. S43.6- may apply | Injury site, laterality, encounter type |
Validate against the CMS FY2027 Addendum before pushing changes into a production system.
The four revised ICD-10-CM descriptions
Four existing codes keep their numbers and get new wording. Neither additions nor deletions, and easy to miss.
| Code | FY2026 description | FY2027 description |
|---|---|---|
| L02.232 | Carbuncle of back [any part, except buttock] | Carbuncle of back [any part, except buttock and flank] |
| L03.312 | Cellulitis of back [any part except buttock] | Cellulitis of back [any part except buttock and flank] |
| L03.322 | Acute lymphangitis of back [any part except buttock] | Acute lymphangitis of back [any part except buttock and flank] |
| Z29.14 | Encounter for prophylactic rabies immune globin | Encounter for prophylactic rabies immune globulin |
Z29.14 corrects a spelling error. Nothing to do.
Act on the three flank revisions. L03.31A (cellulitis of flank) and L03.32A (acute lymphangitis of flank) already existed in FY2026, but the "back" titles did not exclude the flank, so flank cases were landing in L03.312 and L03.322. The revised titles close that gap, and FY2027 adds L02.237, carbuncle of flank. If your dermatology or wound-care coders have been assigning flank cellulitis to L03.312, the FY2027 code is L03.31A.
FY2027 ICD-10-CM Official Guidelines
The FY2027 ICD-10-CM Official Guidelines for Coding and Reporting apply from October 1, 2026 through September 30, 2027. NCHS marks narrative changes in bold and underlines items that moved since the April 2026 FY2026 version.
Code-set changes and guideline changes are separate releases. A team that loads the new code file and keeps last year's guidelines in its training material is still coding to FY2026 rules. Review every bold passage with your coding educators before closing out October training.
One guideline rule did not change and governs every FY2027 specificity split. Under Section I.B.13, when the record does not identify the side, coders assign the unspecified-side code, and the guidelines say unspecified-side codes should rarely be used. Laterality may come from other clinicians' documentation; conflicting documentation goes to a provider query.
What documentation should coders look for in FY2027?
FY2027 asks the same nine questions over and over.
- Right or left. Osteomyelitis, plantar fasciitis, plantar fascial fibromatosis, interstitial and cornual ectopic pregnancy.
- Anatomic site. Skull vs face and sinuses for osteomyelitis. Maxillary, ethmoid, frontal or sphenoid for the new odontogenic sinusitis codes (J34.830 to J34.839). Back vs flank for the revised L-codes. Larynx, pharynx or oral cavity for secondary malignancy.
- Disease subtype. Familial-genetic vs other dilated cardiomyopathy. Arrhythmogenic vs other cardiomyopathy. Brugada vs bigeminy. Glanzmann thrombasthenia vs other platelet defect.
- Named genetic syndrome. Lynch, Li-Fraumeni, Loeys-Dietz, VEXAS, or a pathogenic BRCA1 or BRCA2 mutation.
- Exact BMI. Not a range. The calculated value decides between Z68.18 and Z68.19.
- Named substance. Alkene, cycloparaffin, or other organic solvent.
- Pregnancy location and fetus. Interstitial, cornual, cervical or cesarean scar. With or without an intrauterine pregnancy. Which fetus, for the vanishing twin codes.
- Type of exposure. Gadolinium, burn pits, Agent Orange, or blast overpressure and its level.
- Type of personal history. Social, medical or surgical transition. Intersex surgery. Detransition.
One rule governs all nine and did not change for FY2027. A more specific code does not create documentation that is not in the chart. The FY2027 Official Guidelines still require the highest level of specificity the record supports.
If the operative note does not establish a side, the unspecified code is the honest answer. Query when a query is appropriate. The existence of M86.8X11 is not evidence that the surgeon operated on the right shoulder.
What should coding managers and RCM companies do?
Four steps, in order. For an RCM operation supporting many clients, step 1 sizes the problem before anyone touches a template.
| # | Action | What it gives you |
|---|---|---|
| 1 | Run the 12 affected code families against the last 12 months of claims | Exposure by client, facility, provider and specialty |
| 2 | Search the systems that do not update with the code file | EHR diagnosis favorites, superbills and charge tickets, provider templates and order sets, scheduling and registration pick lists |
| 3 | Verify the clearinghouse and payer edit-file version | A valid FY2027 code checked against an FY2026 edit file fails and reads as a coding error on a denial report |
| 4 | Monitor unspecified-laterality use through October | A spike in M86.8X19 or other X9 codes points to a defaulting template |
Confirm step 3 before opening a coding audit . Exact-value codes such as Z68.18 belong in a documentation review, not an unspecified-use report.
October 1 should be another coding day for MediCodio AI clients
Annual code-set changes create work because a surprising number of systems depend on somebody remembering to update them.
CODIO AI maintains the active code sets inside the platform. When the FY2027 release became effective, coding ran against the current code set rather than a file somebody last uploaded by hand. Clients do not import the annual ICD-10-CM file into CODIO AI, so:
- New FY2027 codes became available on the effective date
- Codes that are no longer billable are not offered as active billable selections
- Current child-code specificity is part of code selection
- Code-file maintenance, including any April midyear update, is not a task on the coding team's list
No spreadsheet for the coding team to load. No annual code file for a coder to retrain the system on. Nobody should have to ask whether the engine is still running last year's code set.
That does not remove every October responsibility, and it would be dishonest to suggest otherwise. EHR favorites, provider templates, superbills, payer edits and clearinghouse validation logic sit outside CODIO AI and still need review. Every check in the section above applies to MediCodio AI clients as written. What changes is that the coding engine is not one of the systems you have to go check.
What happens when documentation does not support the new specificity?
A new ICD-10-CM code does not create documentation that is not in the chart. The official rules still decide the answer.
Complete charts flow through AutoPilot for fully autonomous coding. Charts where the documentation is thin or contradictory stay in CoPilot, where certified coders review and finalize the output.
FY2027 specificity tests that routing directly. If the classification now distinguishes right from left and the note does not establish a side, CODIO AI should not invent one because a more specific code exists. The technology does not replace the rulebook. It applies the current one.
Every code ships with its documentation passage and the compliance rule behind it, which gives coding and QA teams a 100% code-level audit trail. In an October QA review, that is the difference between checking a sample and checking the reasoning.
See how FY2027 specificity plays out on your own charts. Book a demo and we will run an accuracy check on a sample of your documentation.
The FY2027 pattern: specificity keeps increasing
FY2027 did not introduce 190 new diseases. It took conditions that lived inside broad categories and gave them their own codes. Right or left instead of a single site. Arrhythmogenic cardiomyopathy instead of "other cardiomyopathies." Brugada syndrome instead of "other specified cardiac arrhythmias." Lynch syndrome instead of a susceptibility status. Alkenes and cycloparaffins instead of "other organic solvents." A BMI of 18.2 instead of "19.9 or less."
For coders, that raises the value of a precise note. For coding managers and RCM organizations, the annual update does not end when somebody downloads a new code file. It ends when the favorites, templates and superbills match it.
FY2028 arrives next October, with a possible April update before it. The code set underneath the work should be the part nobody has to think about.
Sources
Every figure in this article was checked against the official CMS and NCHS FY2027 ICD-10-CM release files.
- CDC/NCHS: ICD-10-CM program page. cdc.gov/nchs/icd/icd-10-cm. NCHS is the maintainer of ICD-10-CM.
- CDC/NCHS: ICD-10-CM files. cdc.gov/nchs/icd/icd-10-cm/files.html. Current release files, including any midyear update.
- CMS: ICD-10 code files. cms.gov/medicare/coding-billing/icd-10-codes. FY2027 Addendum, Code Descriptions, Code Tables and Index, Conversion Table, and the April 1 update files referenced above.
- CMS: FY2027 ICD-10-CM Addendum (ZIP). 2027-icd-10-addendum.zip. Authoritative list of additions, deletions and revisions. The 190 additions, 30 deletions and 4 revised descriptions cited here come from this file, as does the list of 30 affected codes.
- CMS: FY2027 Code Descriptions in Tabular Order (ZIP). 2027-code-descriptions-tabular-order.zip. Source of the 74,879 billable-code total and of every code description quoted above.
- CDC/NCHS: ICD-10-CM Official Guidelines for Coding and Reporting (PDF). ICD-10-CM-October-1-2026-FY27-Guidelines.pdf. Effective-date window, laterality rule, code-selection rules and the specificity requirement referenced above.