Inpatient rehab coding has always posed a challenge to coders, even to those with years of coding experience. Coding for the IRF-PAI is unique as it does not follow traditional coding guidelines and goes against everything that is taught in school. Most HIM and coding programs offer courses that teach traditional coding applicable to acute care, ambulatory or an outpatient setting. There is very limited education available to coders that also code rehab accounts as part of their job. For IRF accounts, an instrument called the IRF-PAI is completed on admission and discharge. This helps determine the payment for the case as well as the estimated length of stay for the patient. Along with other data items, the impairment group code and ICD-10-CM codes for the etiology, comorbid conditions and complications are entered on the IRF-PAI. Since the IRF PAI is coded based on IRF-PPS guidelines, coders need to have a basic understanding of these guidelines. If the codes entered on the IRF-PAI are incorrect, this could result in incorrect revenue for the facility and inaccurate estimated length of stay for the patient.