Modifier
Updated September 30, 2026
Definition
A 2-character code added to a procedure code to give more detail about the service, like special circumstances. A modifier can change whether and how much your plan pays.
A modifier is a short add-on to a billing code. It's usually 2 letters or numbers placed right after a CPT or HCPCS code. It tells your plan something the main code doesn't, like a special circumstance during the service.
For example, the modifier "NU" marks new medical equipment, and "UE" marks used equipment. Other modifiers can show that 2 services on the same day were separate. A missing modifier can lead to a denial or a higher share for you, and an extra one can lead to a charge worth questioning.
You'll see modifiers next to the codes on an itemized bill. If a line was denied or costs more than you expected, ask the billing office to check the code and modifier. Our guide to common medical billing errors shows other problems to look for.
Related terms
Guides that use this term
- Guide12 common medical billing errors and how to spot themDuplicate charges, wrong codes, missing insurance discounts, and more. Use this checklist of 12 common medical billing errors, then learn how to fix them.
- GuideCharged for a screening colonoscopy? Why and how to fix itA screening colonoscopy should usually cost $0. Learn what it costs, why it gets billed as diagnostic, and how to get your provider and plan to fix it.
Sources
- Overview of coding & classification systems, Centers for Medicare & Medicaid Services. Accessed September 30, 2026.
- Proper use of modifiers 59, XE, XP, XS & XU (MLN1783722), Centers for Medicare & Medicaid Services. Accessed September 30, 2026.
This is general information, not legal or medical advice. Rules can depend on your plan and your state. Romi Care isn't an insurer, law firm, collection agency, or government program.