Modifier 1P is a Category II performance measure exclusion modifier used to indicate that a patient’s medical condition prevented performance of the action specified by a Category II quality measure (for example, a contraindication, absent organ/limb, or documented allergy). It is appended only to Category II codes that explicitly allow this exclusion and must be supported in the medical record. Because Category II codes are used for quality reporting and have no RVUs, 1P does not change payment — it only removes the patient from the measure denominator for reporting purposes.

When a provider considered the measure but could not perform it for documented medical reasons, 1P flags that the patient should be excluded from the pool of patients expected to receive the measure (a denominator exclusion). Examples include recording a Category II code for a medication that was considered but not given because of a documented allergy (e.g., reporting 4016F‑1P) or documenting that a measured assessment could not be completed due to amputation. Use is limited to Category II codes that list 1P as an accepted exclusion modifier; always confirm individual measure guidance.

Because Category II codes carry no direct reimbursement value, appending 1P can improve reported performance rates by appropriately excluding inapplicable patients but does not increase payment. Incorrect or missing exclusion modifiers can lead to inaccurate quality reporting, though they do not directly alter fee-for-service reimbursement.