How Medical Billing Works, Step by Step

Follow a single claim from the visit to the payment. Eight steps, each one a handoff, each handoff a place where the claim can stall or break. This post walks the claim through all eight, in order, with the actual mechanics at each stop.

One scope note. This post starts at charge capture, after the visit is documented. Everything before that, scheduling, eligibility verification, prior authorization, belongs to the front end of the revenue cycle, which we cover in the RCM overview. The claim's journey starts here.

The medical billing process is the sequence that turns a patient visit into payment. Charges are captured and coded (CPT and ICD-10), the claim is scrubbed and submitted to the payer, the payer adjudicates it, and the practice posts the payment or works the denial, then collects any patient balance. Each step feeds the next.

What is the medical billing process?

Three parties, one chain of handoffs. The provider delivers the care and creates the claim. The payer, usually an insurance company, decides what each line on the claim is worth and pays its share. The patient pays whatever the payer assigns to them: deductible, copay, or coinsurance.

The process is the machinery between those parties: turning the visit into codes, the codes into a claim, the claim into an adjudicated payment, and any leftover balance into a collected dollar. Errors compound through that chain, which is why a slip at step one can still be costing the practice at step eight.

The claim lifecycle, in order

1. Charge capture

A visit creates a record: vitals, exam notes, orders, procedures performed. Charge capture turns that record into a list of billable services, each tied to a fee. It sounds automatic. It's not.

What goes missing: a procedure the doctor performed but never documented, a service buried in a progress note that nobody translated into a charge, a supply or facility fee that fell off the sheet. The usual cause is a workflow gap. The physician charts late from memory, the note says "knee injection" with no detail, and the coder cannot tell whether it was one knee or two.

The defense is a daily reconciliation: match the appointment list against the charges entered, and treat every gap as an error to investigate.

2. Coding (CPT and ICD-10)

Every service gets a procedure code and every diagnosis gets a diagnosis code. In the United States that means CPT codes for what was done and ICD-10 codes for why. The two have to pair: the diagnosis must justify the procedure to the payer. A knee X-ray coded with a diagnosis of headache gets denied, because the payer sees no medical necessity. Payers check this line by line.

This work is usually done by certified coders, sometimes by the physician, sometimes by software with a human reviewing the output. Whoever codes works from the clinical documentation, not from memory of the visit. Vague notes produce vague codes, and vague codes produce denials or downcoding to a lower-paying level.

Two ways this step costs money. Code below what the documentation supports and the practice leaves revenue on the table. Code above it and the practice bills for something it cannot defend.

3. Claim scrubbing

Before a claim goes to the payer, it gets checked. That check is called scrubbing, and it runs the claim against a set of edits.

Three kinds. Demographic edits verify the basics: member ID format, date of birth matching the payer's file, a valid service location. Coding edits check the code pairs: does the CPT match the ICD-10, are the modifiers correct, are services the payer bundles together split into separate lines. Payer-specific edits check the rules that one payer enforces and another ignores: a referral number on file, a required attachment, a service the plan excludes.

Generic edits catch formatting problems. Payer-specific edits catch the rules that actually vary, and they are the ones practices trip over. A claim that passes scrubbing is not guaranteed to pay, but a claim that fails it needs fixing before it goes out.

4. Claim submission (837P / 837I)

The finished claim travels to the payer, almost always electronically, through a clearinghouse. The clearinghouse is the middleman. It validates the claim's format, routes it to the right payer, and sends back an acknowledgment that the payer received it. If the clearinghouse bounces the claim, it never reached the payer. That is a rejection, not a denial, and it usually gets fixed and resent quickly.

Claims travel in two formats. Professional claims, from physicians, clinics, and labs, go as 837P, the electronic version of the CMS-1500 form. Institutional claims, from hospitals and surgical centers, go as 837I, the electronic version of the UB-04. Same journey, different paperwork.

5. Adjudication

Adjudication is the payer deciding what each line on the claim is worth. The payer checks that the patient was eligible on the date of service, runs the codes against its medical-necessity rules and the provider's contract, then prices each line. Three outcomes per line: paid, adjusted, or denied.

Paid means the line pays at the allowed amount. That is the contracted rate, not the billed charge. The billed charge is the practice's starting number; the allowed amount is the number the contract sets, and it is almost always lower.

Adjusted means the payer reduced the line to the allowed amount. The difference is a contractual adjustment, and the practice writes it off. It cannot bill the patient for it.

Denied means the payer refused the line and attached a reason code saying why. The payer then sends back a remittance: an electronic 835 file (the electronic remittance advice, or ERA) to the practice, or a paper explanation of benefits (EOB). The remittance lists every line, what the payer did with it, and why.

6. Payment or denial

This is where the claim's path splits in two. On the clean-claim path, the remittance shows payment at the allowed amount on every line, and the claim moves to payment posting. On the denied path, the remittance shows a zero or reduced payment with reason codes attached, and the claim moves to denial work.

Reading the remittance correctly decides which path the claim is on, and misreading it is expensive. A denied line treated as a contractual adjustment gets written off instead of worked. A paid line treated as denied gets reworked for no reason.

The denied path is a normal branch of the process, not an exception to it. A working billing operation expects denials and has a routine for them: read the reason code, fix the problem or appeal the decision, and track the claim until it resolves.

Some claims do not end with the first payer. When a patient has two plans, the first payer's remittance passes the remaining balance to the second, and coordination of benefits decides who pays what.

7. Payment posting

Posting is recording the payer's payment in the practice management system and matching it against what the claim was supposed to pay. Each line on the remittance gets posted: payments to revenue, contractual adjustments to the write-off column, patient responsibility to the patient's balance.

Then comes reconciliation: the posted amounts get compared to the expected allowed amounts, and any shortfall gets flagged. A payer that systematically pays below the contracted rate shows up here as a pattern, not a one-off. That pattern is the evidence a practice needs to dispute an underpayment.

Posting looks clerical. Doing it sloppily is one of the quiet ways money leaks. Unposted payments leave accounts receivable looking unpaid when they are not, and a mismatch nobody investigates becomes a write-off by default.

8. Patient balance and collections

Whatever the remittance assigns to the patient, deductible, copay, or coinsurance, moves to the patient's account, and the practice sends a statement. This happens only after the payer's side is resolved. A denied claim that is still being worked should not generate a patient bill, because the patient does not owe money on a claim the payer has not finished deciding.

Once balances move to statements, the work is follow-up: sending statements on a schedule, answering billing questions, offering payment plans, and knowing when a balance has aged long enough to escalate. That follow-up is accounts receivable work with its own cadence. A/R follow-up covers the mechanics of chasing unpaid balances before they age out.

What happens when a claim is denied?

A denied claim and a rejected claim are different problems. A rejected claim never reached the payer. The clearinghouse or the payer's front door bounced it for a formatting or eligibility error, and it never entered adjudication. Rejections are usually fixed and resubmitted quickly.

A denied claim went through adjudication and the payer said no to one or more lines, with a reason code explaining why. The fix depends on the reason. If the claim was wrong, a bad code, a missing modifier, a wrong date of service, the practice corrects it and resubmits, and the corrected claim goes back through normal processing. If the claim was right and the payer still refused, the practice appeals: it writes up the case, attaches the documentation, and asks the payer to reconsider. Appeals take longer and get tracked separately.

One more clock runs during all of this. Payers set their own filing windows, and a claim that sits unworked can age past its window. A fixable denial that dies because the window closed is a loss the practice caused itself. Denial management firms run this whole loop for practices that cannot staff it.

Where the process usually breaks

Three places where the process quietly breaks, and none of them are exotic.

Sometimes the service happened but never became a charge. The fix is the same daily reconciliation from step 1: match the appointment list against the charges entered, and investigate every gap.

Unscrubbed edits. Payer-specific rules that never got checked before submission. Most of those claims come back for rework, and every round of rework costs staff time a clean claim never needed.

Unread remittances. Denied lines written off as adjustments, underpayments nobody flagged, patient balances billed before the payer side resolved. The remittance is the payer telling the practice exactly what happened, and a billing operation that does not read it is flying blind. A/R follow-up is the discipline of chasing those balances on a schedule.

How long does the medical billing process take?

The shape of the timeline is simple: clean claims move fast, rework stretches everything.

A clean claim typically moves from submission to payment in days to weeks, depending on the payer. Every round of rework adds time: a rejection gets fixed and resent quickly, a denial that needs correction and resubmission takes longer, and an appeal takes longer still. The timeline is set by the payer's processing speed and how much rework the claim needs. Rework is the part the practice controls.

The lever the practice controls is the one this whole post is about: fewer handoff errors, fewer rounds of rework.

Frequently asked questions

What is the medical billing process? The medical billing process is the sequence that turns a patient visit into payment: charge capture, coding, claim scrubbing, submission to the payer, adjudication, payment posting, and collections. Each step hands off to the next, and a break at any handoff delays payment or creates a denial.

What are the key steps in medical billing? The steps, in order: charge capture, coding (CPT and ICD-10), claim scrubbing, claim submission (837P or 837I), adjudication, payment or denial, payment posting, and patient balance and collections. The pre-visit front end, scheduling, eligibility, and prior authorization, sits upstream in the revenue cycle.

How does claim submission work? The coded claim goes to a clearinghouse, which validates the format and routes it to the payer. Professional claims travel as 837P (the electronic CMS-1500); institutional claims travel as 837I (the electronic UB-04). The clearinghouse returns an acknowledgment confirming the payer received it.

What is the difference between medical billing and revenue cycle? Medical billing is the middle of the revenue cycle: coding, claim submission, denial management, payment posting, and collections. The revenue cycle includes all of that plus the front end: scheduling, registration, eligibility verification, and prior authorization. Billing is one stretch of the cycle, not the whole thing.

How long should the medical billing process take? There is no single standard; timelines vary by payer, service type, and whether the claim is denied. A clean claim moves through in days to weeks. A denied claim that needs correction or appeal takes longer. Every round of rework stretches the timeline further.

What is a clean claim? A claim that is complete and accurate on the first pass: correct demographics, codes that pair with the diagnosis, and all payer-specific requirements met. It passes the payer's edits without rework and pays at the allowed amount. Every step after a clean claim is just processing; a dirty claim starts a rework loop.

The pre-visit front end is covered in our RCM overview, and our methodology explains how the firms in this directory are evaluated.