You spent years learning how to treat patients. Nobody spent an hour teaching you how the money for that care reaches your bank account. That gap is why so many new practices spend their first year staring at denied claims with no idea what went wrong.
Most doctors leave training without a single lecture on billing, so the question “what is medical billing” usually gets answered the hard way. This guide answers it in plain language. It covers how a claim moves from check-in to payment, where money leaks along the way, and what to do about it.
At Claimstone Billing, we work with healthcare and dental practices across the United States, and the same handful of billing mistakes show up again and again. Every one of them is fixable once you know where to look.
Medical billing in plain terms
Medical billing involves converting a patient visit into a compensated insurance claim. A provider is documented, converted to standardized codes, submitted to the insurance company and tracked until funds are received. When the insurance company doesn’t pay what you think it should or when they say that they won’t, someone has to pursue them. Any deductible or copay that the patient has to pay is out on a patient statement regardless of what the insurance company says.
Billing and coding are commonly confused terms. Coding assigns the codes that describe the visit. Billing takes those codes, builds the claim, and collects on it. Errors in either one show up the same way: late or missing money. A practice can deliver excellent care all day and still struggle to make payroll if the space between care and cash leaks.
How a claim travels from check-in to payment
Every claim follows roughly the same path. Knowing the steps tells you where to look when payments slow down.
- The front desk collects demographics, insurance details, and a copy of the insurance card. One wrong digit in a member ID can sink a claim before the patient reaches the exam room.
- Staff verify that coverage is active on the date of service and check whether the plan requires a referral or prior authorization. A missed authorization causes a denial that perfect coding cannot fix.
- The provider documents the visit. The note has to support every service billed. If it is not in the note, an auditor will treat it as if it did not happen.
- If it’s not in the note then an auditor will consider it not to have happened.
- The coder reviews the note and applies diagnosis codes (ICD-10-CM), procedure codes (CPT and HCPCS Level II) and modifiers. ICD-10-CM alone has over 70,000 codes and CPT has about 10,000.
- Before the claim leaves, charges are entered into the practice management system and the claim is validated for missing fields, conflicting codes, mismatched modifiers, etc. This is called a claim scrub .
- The claim goes to the payer (usually through a clearinghouse). Electronic claims are submitted on the electronic equivalent of the paper CMS-1500 form called the 837P.
- The claim is at the discretion of the payer whether they will pay it, lower the claim, or deny the claim. An electronic remittance advice (835) is sent to the practice and an explanation of benefits is provided to the patient.
- Payment gets posted against the claim, with adjustments for the contracted rate. Anything unpaid becomes accounts receivable.
- Denied claims get corrected and appealed, and patient balances go out on statements.
Who does the billing: in-house, outsourced, or both
Practices handle billing in three ways. Some hire staff and do it in-house. Some hand the whole cycle to a billing company. Others break it up, with registration and eligibility up front and an outside team for coding, submission and follow-up.
In-house billing means control and a person down the hall. It means salary, benefits, software, training, and one point of failure too. When your only biller goes on leave or resigns, claims stop going out and cash flow slows down within weeks. When you outsource your billing, that risk is spread across a team, meaning one resignation won’t halt your revenue. Your choice will depend on your volume of claims, your specialty and how much billing experience your current staff has.
Why claims get denied, and what a denial costs
Denials are where most billing money disappears.According to Experian Health’s 2025 STATE OF CLAIMS SURVEY amassing 250 health care finance and billing professionals, 41 percent now report that denials are 10 percent or more. This figure has increased over the past year since the survey began in 2022. The top three reasons cited by respondents were missing or inaccurate data, authorization issues, and incomplete patient information.
None of those three has anything to do with clinical care. They are front-desk and paperwork errors, which is good news, because paperwork errors can be fixed.Run the math on your own practice. At a 10 percent denial rate, a practice sending 1,000 claims a month has 100 claims that need rework. Each one takes staff time to find the cause, correct it, and resubmit.
Deadlines raise the stakes. Medicare gives providers 12 months from the date of service to file a claim. Commercial payers set their own windows in each contract, and many are much shorter. A denial that sits in a drawer past the filing deadline is money you cannot get back.
Six billing mistakes that quietly cost practices money
These come up in practice after practice:
- Checking eligibility on the day of the visit, which leaves no time to fix a lapsed policy or get an authorization.
- Writing vague documentation that forces the coder to guess, which usually ends in billing a lower level of service than the provider delivered.
- Leaving off modifiers or applying the wrong ones, which gets claims denied or paid at reduced rates.
- Working denials only when someone has spare time, so older claims drift toward their filing deadline.
- Waiting for the statement to collect patient balances instead of asking for the copay at check-in.
- Skipping the monthly report, so a rising denial rate goes unnoticed for a full quarter.
Each fix comes down to a habit and one person who is responsible for it.
The four numbers to check every month
A practice that reads four numbers each month will spot most billing problems early.
The first is the clean claim rate, the share of claims accepted and paid on first submission with no rework. Many billing teams target 95 percent or higher.
The second is the denial rate, the share of submitted claims that payers deny on first pass. Compare yours with the 10 percent line from the Experian survey above. If you are over it, start with the top three denial reasons.
The third is days in accounts receivable, which is the average number of days to get paid for a service provided. A typical goal is under 40 days but specialty mix and payer mix vary what is achievable.
The fourth is the net collection rate, which measures the proportion of ‘collectible’ revenue that the practice actually collects, after the contractual write-off. Again, the common goal is 95 percent or above.
Ask whoever handles your billing for these four every month. If they cannot produce them, you have found your first problem.
What good medical billing support looks like
If you decide to bring in outside help, judge it by what lands in your bank account. A good billing partner should deliver faster payment on claims that are right the first time, fewer denials thanks to front-end checks, follow-up on the ones that slip through, and reports you can read without a translator.
Ask these questions before you sign:
- Who codes my claims, and what credentials do they hold?
- Will you sign a HIPAA business associate agreement?
- Which reports will I get each month, and will they include denial rate and days in A/R?
- Do you learn my payer mix and documentation habits before you touch a claim?
- Who owns the data, and can I leave with it?
- Can I talk to a named person when something goes wrong?
Get the fee structure in writing too, including what it covers and what costs extra. A partner who answers all of this plainly has usually done it before. One who dodges any of it is telling you something.
Where to go from here
Medical billing is the system that decides how much of the care a practice delivers turns into revenue. Practices that run it with owners, numbers, and deadlines collect more and worry less.
Claimstone Billing handles eligibility checks, charge review, coding support, claim submission, payment posting, denial follow-up, and patient balance questions for practices across the United States, and our team brings 10+ years of collective experience to that work. Some practices hand us the whole cycle. Others want help with one part, like aging claims. Either way, we learn your payer mix and workflows before we touch a claim. Send us your last three months of billing reports, and we will show you where claims are getting stuck.
Medical billing FAQs
- Medical coding vs medical billing?What is the difference between medical coding and medical billing?
Medical coding turns the provider’s documentation into standard codes for diagnoses, procedures, and supplies. Medical billing paints those codes, constructs the claim, submits it, and then tracks it for payment. In a small practice, it’s possible to perform both, however the methods are different. The coders must have a great understanding of code rules and documentation. Billers must be familiar with the policies and timelines of the payers, and how to work a denial.
- How long does it take to get paid after a claim is submitted?
This is dependent upon the payer. Generally, Medicare will pay clean electronic claims within 30 days, and no sooner than the 14th day after the claims are received. There is a wide range of timelines, depending on the commercial contracts and the prompt payment laws in the state. Check on the status of a claim if it’s been 30 days since the claim was submitted and it hasn’t been paid.
- What is the definition of a clean claim?
A clean claim is one that contains no errors, missing fields, or missing documentation, and the payer doesn’t need to request anything more. Having a high first-pass clean claim rate will lead to fewer claim denials and quick cash. Clean claims are the result of proper front-end work – accurate registration, eligibility verification, codes.
- What happens if an insurance company refuses to pay out on a claim?
The practice accesses the denial reason on the remittance advice, corrects the issue and either resubmits the claim or appeals the denial. Typographical mistakes such as a wrong member ID are typically indicators of a corrected claim. An appeal for medical necessity issues should be made with supporting documentation. Time limits are strict for Appeals. The window for filing a first level appeal (redetermination) is 120 days from the decision for Medicare, and the window will vary by commercial payers in the contract.
- Should a small practice have their medical billing done for them?
It’s often a good idea, not to mention it’s one biller to rule them all. Denials are going up, Claims are unpaid for more than 60 days, or the owner is billing at night, the case becomes stronger. If you’re satisfied with your current biller, and your four month numbers are in good shape, you might be better off just sticking with them.
- What is the cost of medical billing?
Typical billing companies might charge a percentage, a flat monthly fee, or a per claim rate. It depends upon specialty, claim quantity and the part of the cycle which the company manages. There are some costs associated with in-house billing; salary, benefits, software, clearinghouse fees, and training. Check the overall cost versus overall collections and inquire about the fee before you sign.
- Will outsourced medical billing be HIPAA compliant?
It may be and it must be. A billing company that processes protected health information is a business associate under HIPAA and the practice must have a signed business associate agreement with the billing company. Inquire about the company’s access to records, data storage locations and employee training methods.