Inpatient Rehab Coding Challenges: IRF-PAI vs. UB-04 Coding

by Nirmala Sivakumar, CCS, CDIP

While freestanding rehabilitation hospitals have a dedicated rehabilitation coder, the coding for rehab units within an acute hospital is done by coders that may not be familiar with IRF-PPS coding guidelines. Many HIM professionals that code for the rehab units are not familiar with how IRFs are reimbursed and may assume that payment is based on the Diagnosis Related Group (DRG) generated by the principal diagnosis on the UB-04.

It is essential that HIM Managers and Coders understand IRF-PPS guidelines and the differences in the coding of the two documents, the IRF-PAI and the UB-04. The codes reported on these two documents might differ in some scenarios. However, they must tell the same story on the patient’s reason for admission to inpatient rehab.

Choosing the principal diagnosis on the bill must be accurate and based on physician documentation for the reason for admission and in accordance with coding guidelines. Though the ICD-10 codes reported on the UB-04 do not affect Medicare reimbursement, they still need to be coded accurately.

There is a need for IRF-specific training resources to support both coders and those who depend on their coding:

  • Different coders may interpret guidelines differently, which leads to inconsistencies in coding.
  • Though Prospective Payment System (PPS) coordinators are responsible for the completion of the IRF-PAI, they are not generally proficient in ICD-10 coding. PPS coordinators rely on the coding team to provide accurate ICD-10 codes for the IRF-PAI.

All of these factors combined could lead to inaccurate coding and potentially have an impact on an IRF’s 60% presumptive compliance and reimbursement. Inconsistencies and questionable coding choice can also trigger potential audits.

Get to Know Inpatient Rehab Coding
If you are new to Inpatient Rehab Coding, a few definitions will be helpful:

  • An Inpatient Rehab Facility (IRF) may be either a free-standing hospital or a unit within an acute hospital that offers an intensive rehabilitation program to patients.
  • An IRF is reimbursed through the IRF Prospective Payment System if it meets criteria specified in federal regulations.
  • An IRF’s reimbursement and a patient’s estimated length of stay are determined by a case-mix group (CMG). This classification groups together patients who are expected to use similar resources during their IRF stay.
  • This, along with other patient data, is reported on an instrument called Inpatient Rehabilitation Facility – Patient Assessment Instrument (IRF-PAI) and is submitted to the Center for Medicare and Medicaid Services (CMS).


Inpatient Rehabilitation Facility: IRF-PAI and UB-04 Coding
Inpatient rehab coding presents a challenge for HIM coders, even those with many years of coding experience. While both the IRF-PAI and UB-04 forms are used by Inpatient Rehabilitation Facilities to report ICD-10-CM codes, there are several key differences. This webinar will help the IRF coder gain a clear understanding of IRF PPS guidelines and how ICD-10-CM coding conventions apply to the IRF setting. Learn more here.


Nirmala Sivakumar, CCS, CDIP
Nirmala Sivakumar, is an IRF Coding Educator based in PA. She has created and presented many webinars and workshops on IRF coding and improving clinical documentation. She has trained and mentored many rehab coders. She also has experience in conducting coding audits. She enjoys sharing her expertise and knowledge and has a desire to help coders and PPS Coordinators overcome the challenges of IRF PPS coding.

She has held previous positions as Health Information Management Supervisor for one of HealthSouth’s (Encompass) acute inpatient rehab hospital and as a HIM Coding Consultant at Uniform Data Systems for Medical Rehabilitation. She can be reached at [email protected] or visit

About the Author

Libman Education
Libman Education Inc. is a leading provider of training for the health care workforce offering self-paced and instructor-led online courses designed and developed by leading industry experts in Health Information Management (HIM) and Medical Record Coding. Our courses are specifically designed to improve individual skills and increase the efficiencies and competencies of health care providers and institutions. At Libman Education, we understand the needs and challenges of a well-trained workforce and offer the right-mix of online education to ensure that the health care professionals are prepared to meet the challenges of the changing workplace.

One thought on “Inpatient Rehab Coding Challenges: IRF-PAI vs. UB-04 Coding

  1. Mary Jo Morelli, RHIT - September 25, 2020 at 11:09 am

    So happy you are offering this. Nirmala is very knowledgeable and I used to really enjoy the information she shared presented with UDS.I will be purchasing!