HHAs that run a Part B outpatient therapy business that goes into patients' homes should watch out for some common billing problems. The Comprehensive Error Rate Testing (CERT) program found four major errors among outpatient rehabilitation therapy service claims. The main issues: missing/incomplete plan of care/treatment plan; missing physician/non-physician practitioner (NPP) signature and dates; missing modality time; and missing certification and recertification, according to a CMS fact sheet. Tip: When you report a CPT code for therapy services, double-check to determine whether CPT classifies it as a time-based code or not. Many therapy modalities are billed in 15-minute increments, and "the last unit may be counted as a full unit of service if at least eight minutes of additional service has been furnished," CMS says in the document. The fact sheet is at www.cms.gov/MLNProducts/downloads/Outpatient_Rehabilitation_Fact_Sheet_ICN905365.pdf.