What Is Medical Billing? A Guide for U.S. Practices

Medical billing in simple terms

Medical billing connects the clinical record to the financial record. The work begins before a visit, when demographic, coverage and authorization details are collected, and continues after a claim is sent, when acknowledgements, remittance information, denials, payments and remaining balances must be resolved.

Billing is not simply data entry and it is not the same as bookkeeping. A reliable workflow preserves a traceable path from the service that was documented to the codes reported, the claim transmitted, the payer decision received and the balance shown in the practice system.

Medical billing and medical coding are connected, but different

In practice, coding and billing depend on one another. A technically valid claim can still be wrong if documentation or code selection is unsupported. A correctly coded service can still fail if enrollment, eligibility, claim data or transmission rules are wrong.

The medical billing process, step by step

1. Register the patient and coverage. Capture accurate identity, contact, insurance and coordination-of-benefits information using the practice's approved process.
2. Verify eligibility and benefits. Check the relevant payer response and identify authorization, referral or coverage questions before the service when possible.
3. Document and capture the service. The clinical record must support what occurred; the charge workflow must include the correct provider, location and date.
4. Assign and review codes. Apply the code sets and payer instructions that are effective for the date and setting of service.
5. Create the claim. Populate the professional, institutional or dental claim with the required patient, provider, payer, service and coordination information.
6. Run edits and submit. Check required fields and known edits, then transmit through the practice's clearinghouse or payer channel.
7. Confirm acceptance. A clearinghouse or payer acknowledgement is not the same as payment. Rejected files or claims must be corrected through the appropriate workflow.
8. Review adjudication. The payer may pay, deny, reduce, pend or request information according to coverage, contract and claim rules.
9. Post and reconcile. Match the remittance and funds to the correct claims and service lines, post supported adjustments, and reconcile deposits and exceptions.
10. Resolve open balances. Work denials, claim status, underpayments, credits and patient responsibility with documented ownership and deadlines.

A fictional claim walkthrough

Example only—no patient, payer, code or payment amount is real. A U.S. physician practice schedules a follow-up visit. Staff confirm the patient's current coverage and record the payer response. After the visit, the clinician completes the note. The coding step selects codes supported by the documentation and the rules effective for that date of service.

The billing system creates a professional claim and sends it in the adopted electronic claim format through the practice's clearinghouse. The team first checks acknowledgement reports to confirm whether the file and claim were accepted for payer processing. After adjudication, the payer returns remittance detail. The posting workflow associates each decision and adjustment with the submitted service line and reconciles the payment. Any supported patient responsibility follows the practice's policy; any rejection, denial or unexplained balance goes to the correct work queue.

The useful control is the chain of evidence: source documentation → code selection → submitted claim → acknowledgement → payer decision → posting and reconciliation → next action.

The transactions behind the workflow

HIPAA Administrative Simplification standards create a common electronic structure for many routine exchanges. For non-pharmacy health claims, HHS adopted ASC X12N 837 Version 5010; CMS lists January 1, 2012 as the standard's compliance date. The same CMS table identifies 270/271 for eligibility, 276/277 for claim status and 835 for claim payment or electronic remittance advice.

Current code-set dates matter

Code files change on defined schedules, so the correct source depends on the service, setting and date. CMS states that FY 2027 ICD-10-CM and ICD-10-PCS updates apply to patient encounters or discharges on and after October 1, 2026. CMS also posted the October 2026 HCPCS Level II file on September 23, 2026.

• Do not apply a new code merely because a future file is available.
• Confirm the effective date, care setting and payer instruction.
• Use the applicable official code source, coverage policy and contract—not a copied list with an unknown update date.
• For Medicare processing questions, check the current CMS manual and the responsible Medicare Administrative Contractor.

CMS's current Medicare professional-claim booklet is dated December 2025, and its Medicare FFS companion-guide page was last modified April 1, 2026. Those sources explain the national format and point practices to jurisdiction-specific EDI instructions.

Who owns each part of medical billing?

Outsourcing a task does not remove the practice's need for oversight. HHS OIG identifies proper coding and billing, medical necessity and documentation as core physician-practice compliance risk areas.

Common failure points and useful controls

How practices can measure the workflow

No single metric proves that medical billing is healthy. Use a small set of consistently defined measures and trace changes to claim-level evidence.

• Charge lag: time from the service to a complete billable charge.
• Submission acceptance: claims accepted by the clearinghouse and payer intake process.
• Denial rate: define the numerator, denominator and whether rejections are separate.
• A/R aging and days in A/R: review consistent trends plus payer and work-queue detail.
• Payment-posting and reconciliation exceptions: remittances, deposits, unapplied cash and credits awaiting resolution.
• Open-work timeliness: claims approaching payer or appeal deadlines without a supported next action.

ERG's Revenue Lab provides a privacy-safe workflow checkup and fictional sample report. It does not require patient data.

When a practice evaluates billing support

Start with scope rather than promises. Document who owns eligibility, charge entry, coding review, claim submission, denials, payment posting, patient balances, old A/R, reporting and payer access. Then compare the proposed workflow with the practice's actual systems, volume, specialty, payer mix and internal staff.

ERG does not publish public pricing. Pricing is customized to the practice's services and needs. Review ERG's medical billing service scope, then request a practice consultation for a scoped discussion.

Frequently asked questions