Modifier GA. Waiver of liability (ABN) on file, required by payer policy — used when a denial is expected for lack of medical necessity; assigns liability to the beneficiary on denial. Don't combine with GX/GY/GZ.
Reference only — CPT descriptors are AMA-copyrighted (paraphrased). Payment percentages and acceptance vary by payer; verify against the current CPT/HCPCS files and payer policy.