What is OASIS in home health?
The short answer
OASIS is a set of standard questions built into the home health assessment. A registered nurse usually completes it, or a therapist when therapy is the only service ordered. It's done at the start of care, at recertification, after a hospital stay and at discharge, and each time point has a deadline in calendar days. The answers help set what Medicare pays the agency and feed its public star rating. The agency must send each completed assessment to CMS within 30 days.
What OASIS is
The home health assessment includes a set of standard questions called OASIS. It isn't a separate task. The items are answered as part of the assessment, and the agency reports the answers to CMS as quality data.
Fine print
OASIS stands for the Outcome and Assessment Information Set. CMS describes it as "a group of standard data elements home health agencies (HHAs) integrate into their comprehensive assessment, to collect and report quality data to the Centers for Medicare & Medicaid Services (CMS)." The federal rule requires the assessment to include "the current version" of the OASIS items, "using the language and groupings" CMS specifies.
Which patients and which version
OASIS applies to patients of any payer who are getting skilled services, as long as their start of care is on or after July 1, 2025, with a few exemptions. It used to be required for Medicare and Medicaid patients. The current version is OASIS-E2, in force since April 1, 2026.
Fine print
The exemptions, in CMS's words, are "patients under the age of 18, patients receiving maternity services, and patients receiving only personal care, housekeeping and/or chore services." CMS has issued twelve versions since 1999, three of them since 2023. CMS calls OASIS-E2 "a minor revision." It replaced the transportation item, removed the COVID-19 vaccination item, replaced the gender item with a sex item, reworded the answer choices on the falls item, and added the hearing, vision and language items to the assessment done after a hospital stay.
When it's due
Each time point, meaning each occasion when an OASIS is due, has a deadline counted in calendar days. The start of care is due within five calendar days after the start of care date. A resumption of care, a significant change in the patient's condition, a transfer, a death at home and a discharge are each due within two calendar days. Recertification is the last five days of every 60 days.
Most of these need you to see the patient at home. Transfer and death at home collect limited data, and most of it may be gathered over the phone. The data at each time point should come from a fresh assessment, not be carried over from the last one.
Fine print
The full list of time points follows. CMS calls each occasion a time point. On transfer and death at home, CMS says most of the limited data "may be obtained through a telephone call." CMS says the data at each time point should be "based on a unique patient assessment, not simply carried over from a previous assessment." The federal rule on the visit after a hospital stay is worded in hours, and chapter 10 sets the two side by side.
| Time point | When it's due |
|---|---|
| Start of care | Within 5 calendar days after the start of care date |
| Resumption of care, when a patient returns from an inpatient stay | Within 2 calendar days of the facility discharge date, or of learning the patient is home |
| Recertification, when care continues past 60 days | The last 5 days of every 60 days, which is days 56 to 60 |
| Other follow-up | Within 2 calendar days of a significant change in the patient's condition |
| Transfer to an inpatient facility | Within 2 calendar days of the transfer, or of learning about it |
| Death at home | Within 2 calendar days of the death |
| Discharge | Within 2 calendar days of the discharge date |
Who fills it out
At the start of care, a registered nurse completes the comprehensive assessment and its OASIS items. If physical therapy, speech-language pathology or occupational therapy is the only service ordered, a therapist may complete it instead. One clinician is responsible for each assessment. Others may help collect information if agency policy allows and it happens within the assessment's time frame. The agency's software isn't allowed to answer the items or generate a final code for you.
Fine print
For Medicare patients, an occupational therapist may complete it when occupational therapy is ordered along with one of the other two. When nursing and therapy are both ordered, the manual says a registered nurse, physical therapist, speech-language pathologist or occupational therapist may complete the later assessments. The manual says licensed practical and vocational nurses, therapy assistants, medical social workers and aides "may not be responsible for completing the comprehensive assessment and OASIS," and that an agency's software "may not 'answer' or 'generate' a final code for the OASIS items."
What the questions ask
The questions cover areas like hearing, vision and mood, how a patient moves, how they take their medications, and skin. Items have codes. Older ones start with an M and a number, like M1830 Bathing. Newer ones start with a section letter, like GG0130 Self-Care. M2001, Drug Regimen Review, records whether the medication review from chapter 7 was done and whether it found a significant issue.
Fine print
OASIS-E2 has sixteen lettered sections, from Section A, Administrative Information, to Section Q, Participation in Assessment and Goal Setting. Among the others are hearing, speech and vision, cognition, mood, behavior, preferences for routine activities, functional status, bladder and bowel, diagnoses, health conditions, nutrition, skin, medications, and special treatments. Other examples of item names are M1860 Ambulation/Locomotion and GG0170 Mobility. The set also includes a short cognition interview and a mood interview. On time, CMS's current forms estimate 0.15 to 0.3 minutes for each data element on the form, which includes the time to review instructions and gather the data. The forms no longer print a total in minutes for each assessment. CMS publishes the OASIS-E2 guidance manual on its website. Chapter 1 holds the conventions and the deadlines, and each item comes with a note on its intent.
How to answer
When you answer, think about the day of the assessment, unless the item names a different period. If the patient's ability or status varies during that time, report what's true more than 50% of the time, unless the item says otherwise. Base answers about current status on what's observed and reported at this assessment, not on earlier ones. A few items do call for reviewing documentation, and for physiological or functional status direct observation is the preferred strategy. A dash means no information was available, and dashes are expected to be rare. At the start of care, Section GG has its own rule: the code reflects the patient's baseline ability, before the agency's services helped.
Fine print
CMS calls these general rules conventions. It defines the day of assessment as "the 24-hour period directly preceding the assessment visit, plus the time the clinician is in the home conducting the assessment." On status, it says "direct observation is the preferred strategy." On dashes: "CMS expects dash use to be a rare occurrence." For Section GG, the code reflects "the patient's baseline ability to complete the activity, prior to the benefit of services provided by agency staff."
Where your answers go
The answers help set what Medicare pays the agency, because the functional impairment level, a low, medium or high rating, comes from them. They feed the agency's public star rating for quality of care, along with Medicare claims data. They also count toward a payment adjustment for eligible agencies under a national program, based on their quality results. All of it depends on accuracy: whatever you record has to accurately reflect how the patient was at the time of the assessment.
| Where the answers go | What they do |
|---|---|
| What Medicare pays the agency | The functional impairment level, a low, medium or high rating, comes from them. It is one of five things that sort each 30-day period into one of 432 payment groups |
| The agency's public star rating for quality of care | They feed it, along with Medicare claims data. It uses seven measures, among them improvement in walking, in getting in and out of bed, in bathing, in shortness of breath and in managing oral medications |
| A payment adjustment for eligible agencies under a national program | They count toward it, based on the agency's quality results. The adjustment is a percent from -5% to 5%, and six of the measures come from OASIS |
| All of it | Depends on accuracy. Whatever you record has to accurately reflect how the patient was at the time of the assessment |
Fine print
Medicare sorts each 30-day period into one of 432 payment groups using five things: where the patient was admitted from, whether the period is early or late, the clinical group (which comes from the diagnosis), the functional impairment level, and other health conditions. CMS says the functional impairment level "is determined by responses to certain OASIS items associated with activities of daily living and risk of hospitalization," naming items M1800 to M1860 and M1033. The star rating for quality of care "is based on OASIS assessments and Medicare claims data." It uses seven measures, among them improvement in walking, in getting in and out of bed, in bathing, in shortness of breath and in managing oral medications. CMS builds the OASIS measures from an episode that begins at the start or resumption of care and ends at discharge, transfer or death. The adjustment is "an applicable percent ranging from -5% to 5%," and six of the measures come from OASIS. Separately, an agency must submit at least 90% of its required OASIS records each year, or its annual payment update is cut by 2 percentage points. The data "must accurately reflect the patient's status at the time of assessment."
How accurate the data is
Federal auditors have checked one slice of the data, falls with major injury, to see how complete it is.
Fine print
A 2023 federal audit by the Office of Inspector General found that 55% of the falls with major injury it identified in Medicare claims were missing from the OASIS assessments that should have reported them. It compared Medicare hospital claims for falls with major injury against OASIS and reported: "Fifty-five percent of falls we identified in Medicare claims were not reported in associated OASIS assessments as required."