Unbundling
Updated September 30, 2026
Definition
Billing separate codes for parts of a service that should be billed under 1 combined code. It can raise the total, so it's a coding question worth asking about.
Unbundling happens when a bill lists separate codes for parts of a service that should be billed under 1 combined code. Medicare's coding rules say providers should use the most complete code that describes the service. Billing the parts separately usually costs more.
For example, a mammogram of both breasts has its own code. Billing it as 2 one-side mammograms is unbundling. Say each one-side line is $250, for a total of $500, and the combined code is $350. That's $150 more than the correct code.
Unbundling is often a coding mistake, and not every separate line is wrong. Some services can be billed separately, sometimes with a modifier. If you see several lines that look like parts of 1 service, ask the billing office to check the coding. Our guide to common medical billing errors shows what 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.
- GuideHow to dispute a medical bill: steps and letter templateThink your medical bill is wrong? Here's how to dispute it: what to check, what to say, what to put in a letter, and where to turn if you're stuck.
Sources
- Medicare NCCI policy manual, Chapter 1: General correct coding policies (2026), Centers for Medicare & Medicaid Services. Accessed September 30, 2026.
- National Correct Coding Initiative (NCCI) edits, 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.