That extra point bumps the HIPPS code up from a "J" or "L" in the fourth position to a "K" (without therapy) or "M" (with therapy). That results in an extra $200 for a non-therapy patient and an extra $600 for a therapy patient.
Underpayments occur when the reverse happens--agencies mark a hospital stay without a rehab or SNF stay when one occurred. This is a common error when patients switch bed types within a hospital, experts note.
Source: HHS Office of Inspector General, http://oig.hhs.gov/oas/reports/region1/10300500.pdf