MedicaidBilling CodesMedium impact
Correction to Home Health (Acute Care Services) Billing Guide
Washington Apple Health·WA · Occupational Therapy·Billing Guide
Effective date
Jan 21, 2022
We identified it
Jun 20, 2026
Summary
The Washington State Health Care Authority corrected the modifier for outpatient occupational therapy assistant services in home health acute care billing. The correct modifier is CO, not GO, effective January 21, 2022.
Action Required
Immediately: Billing team must update billing system to use modifier CO (not GO) for all outpatient occupational therapy assistant services in home health acute care settings. Update encounter forms and billing templates. Review and resubmit any recent claims that used the incorrect GO modifier.