Medical billing rules: the rules library
Medical billing rules come from four places that stack: federal law and CMS policy, the Medicare Administrative Contractor (MAC) that pays your claims, state law, and each payer's own contract. This library has one page for each rule we cover, grouped by the kind of problem it causes.
Written by Salman Saeed, CEO and Co-Founder · Reviewed by a Certified Medical Coder · Last reviewed October 2026
Claims and filing
Coding and edits
Hospital and facility payment
Emergency, observation and admission
Compliance and patient notices
How do federal, MAC, state and payer rules fit together?
Four layers apply to most claims, and the layer closest to the payment usually decides the outcome. Federal rules set the floor for Medicare, while state law and payer contracts add their own limits for everyone else.
| Layer | What it covers | Where to read it |
|---|---|---|
| Federal law and CMS policy | Medicare filing, appeals, overpayments, admission and payment rules | eCFR Title 42 and the CMS manuals |
| MAC coverage decisions | Local coverage determinations (LCDs) and billing articles for your jurisdiction | Medicare Coverage Database |
| State law | Prompt pay deadlines and interest for fully insured plans | State insurance department and statute |
| Payer contract and manual | Filing limits, proof of timely filing, corrected claims | The payer's provider manual and your agreement |
The CMS Medicare Coverage Database explains that LCDs cannot contradict national coverage determinations (NCDs). They exist to clarify an NCD or address common coverage issues. Under 42 CFR 405.1060 an NCD is binding on an administrative law judge, while 42 CFR 405.1062 gives an LCD substantial deference but does not make it binding.
The CMS NCCI Policy Manual states that NCCI program policies and edits do not supersede any other CMS national coding, coverage or payment policies. So an NCCI edit is one rule among several, not the whole answer.
Medicare is not the only rule set on a claim. Under 42 CFR 422.101, Medicare Advantage organizations must comply with NCDs and local contractor written coverage decisions. Medicaid has its own prompt pay standard in 42 CFR 447.45: 90 percent of clean claims from practitioners within 30 days of receipt.
State prompt pay laws do not reach every plan. The Missouri Department of Commerce and Insurance says state laws, including the prompt pay law, do not apply to self-insured employers and health and welfare benefit plans. The prompt pay laws by state page lists the deadline and interest for each state we cover.
For commercial payers the contract governs. UnitedHealthcare's administrative guide says its timely filing limits vary based on state requirements and contracts, and tells providers to refer to their agreement. See timely filing limits by payer for the payer-by-payer detail, and the payer guides for each payer's own manual.
Which billing rule do I need?
Pick the group that matches the problem on your desk. Each page gives the rule in plain words, the form field or modifier it touches, the denial that follows it and the official source.
The code behind a rule is in the code library. State prompt pay detail is on the state pages, and surprise-billing rules are in the No Surprises Act hub. To see where a rule is costing you money, our denial management service traces each denial to the rule that caused it, and revenue cycle management covers the full cycle. To talk it through, book a call.
Common questions
Straight answers from the team that does the work.
Ask a billing lead directly. A 20-minute call, Monday to Friday, 9am to 5pm Eastern.
01Where can I find official Medicare billing rules?
Medicare billing rules sit in four official places. Federal regulations are in Title 42 of the eCFR, claim instructions are in the CMS manuals such as the Claims Processing Manual, coverage rules are in the Medicare Coverage Database, and coding edits are in the CMS NCCI Policy Manual. Each rule page here links to the exact section.
02How often do CMS billing rules change?
Some change on a yearly cycle and some only by rulemaking. CMS publishes the NCCI Policy Manual as a yearly edition, and hospital outpatient payment changes arrive through the annual OPPS final rule, such as the calendar year 2026 drug administration change in site-neutral payment. Check the publisher's current text before you bill.
03Do Medicare billing rules apply to commercial payers?
Not automatically. Medicare rules bind Medicare fee-for-service, and Medicare Advantage plans must follow NCDs and local contractor coverage decisions under 42 CFR 422.101. A commercial payer follows its own contract and provider manual. UnitedHealthcare, for example, says its filing limits vary by state and contract.
04Which billing rules matter most for hospitals and ERs?
For admissions, the two-midnight rule in 42 CFR 412.3 and the observation and MOON notice rules matter most. For payment, OPPS, MS-DRGs and the 3-day payment window decide what bundles. For the ER itself, EMTALA limits what registration may ask, and ED facility level coding sets the visit level.
05How do I know a billing rule is current?
Read it from the publisher, not from a summary. Use the current eCFR text for regulations, the revision date and number on a CMS manual chapter, and the effective date in the Medicare Coverage Database for an LCD. Our rule pages show the date they were last reviewed and list the sources checked.
06Who is responsible for compliance with billing rules, the provider or the billing company?
Both carry duties. Under 42 CFR 401.305 the report-and-return duty for a Medicare overpayment falls on the person who received it, which is the provider or supplier that was paid. Under HIPAA a billing company handling patient data is a business associate and can face civil money penalties itself. Your contract splits the rest.
A denial you cannot trace to a rule?
Book a call and a certified coder will find the rule behind it.