Billing insurance for physical therapy involves a consistent sequence: verify the patient’s coverage, document each visit thoroughly, assign the correct diagnosis and procedure codes, and submit a clean claim. Each step has specific requirements that determine whether you get paid promptly or face denials and delays. Whether you’re opening a new practice or tightening up an existing billing workflow, here’s what the process looks like from start to finish.
Get Credentialed Before You Bill
Before you can bill any insurance company, you need to be credentialed with that payer. This means the insurer has verified your license, education, and practice location and has agreed to include you in their network. The process starts with obtaining a National Provider Identifier (NPI) number, then completing a CAQH profile, which serves as a universal application that most commercial insurers pull from.
Medicare enrollment is a separate process from commercial insurance and typically takes 15 to 35 days, with the ability to backdate claims to your enrollment date. Private insurance credentialing is slower. Most commercial carriers take 60 to 120 days to process an application, and the full contracting process generally runs 3 to 6 months for new contracts. If you’re adding a provider to an existing group contract, it can be shorter. You need a physical practice location in place before most insurers will process your application. Plan for this timeline well before you expect to see patients under insurance coverage.
Verify Benefits and Get Authorization
The revenue cycle starts at the first point of contact with the patient, not at the time of treatment. Before the initial evaluation, verify the patient’s insurance benefits: how many PT visits are covered per year, whether a referral from a physician is required, what the copay and deductible amounts are, and whether the plan requires prior authorization for therapy services.
Prior authorization is one of the most common reasons claims get denied. Some plans require it before treatment begins, while others require it after a set number of visits. If you skip this step and the plan required it, the insurer can refuse to pay the entire claim regardless of how well you documented the visit. Build verification and authorization checks into your intake process so nothing falls through the cracks. Laying out the payment process with the patient at check-in also reduces confusion about their financial responsibility later.
Document Medical Necessity
Insurance companies pay for services that are medically necessary, and your clinical documentation is the evidence. Every visit needs a note that supports why the patient needed skilled physical therapy on that specific date. The standard format is the SOAP note (subjective, objective, assessment, plan), and each section plays a role in justifying reimbursement.
CMS guidelines for documenting medical necessity emphasize several elements: the tests and measures you performed, your clinical assessment, the interventions you chose and why, any changes to the plan of care, and what you taught the patient along with their ability to follow through. Simply listing exercises isn’t enough. Your notes should show the complexity of what you did and why a skilled therapist was needed rather than, say, a home exercise program alone. If an insurer audits your claims, the documentation is what determines whether you keep the money or pay it back.
The plan of care itself needs to include measurable goals with expected timelines, the frequency and duration of visits, and a clear connection between the patient’s diagnosis and the services you’re providing.
Assign the Right Diagnosis Codes
Every claim requires at least one ICD-10 diagnosis code that explains why the patient is receiving therapy. The first-listed code should be the condition chiefly responsible for the services provided on that date. If the patient has additional relevant conditions (for example, diabetes affecting wound healing alongside a knee replacement), list those as secondary codes.
For injury-related cases, external cause codes can be added to describe how the injury happened, but they can never be listed as the primary diagnosis. The injury code always comes first. You can assign as many external cause codes as needed to fully explain the situation, but the primary slot belongs to the condition you’re treating.
Choosing diagnosis codes that are too vague or that don’t match the services billed is a common trigger for denials. Use the most specific code available. “Knee pain” and “ligament sprain of the right knee, initial encounter” tell very different stories to the insurance company reviewing your claim.
Code Your Services Accurately
Physical therapy services are billed using CPT codes, and most fall into two categories: timed codes and untimed codes. Timed codes are billed in 15-minute units and include the treatments that make up the bulk of most sessions, such as therapeutic exercise (97110), gait training (97116), manual therapy (97140), and therapeutic activities (97530). Untimed codes are billed per encounter regardless of how long they take, such as evaluations and re-evaluations.
For timed codes, Medicare uses the “8-minute rule” to determine how many units you can bill. You need at least 8 minutes of a service to bill one unit. The conversion works like this:
- 8 to 22 minutes: 1 unit
- 23 to 37 minutes: 2 units
- 38 to 52 minutes: 3 units
- 53 to 67 minutes: 4 units
When you provide multiple timed services in one session, you total all the timed minutes and apply the rule to determine the overall number of units. If there’s one final 15-minute unit left to allocate, it goes to whichever service had the most remaining minutes. Commercial insurers may follow different rules (some use a stricter “midpoint” rule requiring at least 8 minutes per individual code), so check each payer’s policy.
Submit a Clean Claim
Most outpatient physical therapy claims are submitted on a CMS-1500 form (or its electronic equivalent). A “clean claim” is one that has all required fields filled in correctly the first time, which speeds up cash flow and reduces the cost of reworking rejected claims. The key fields include:
- Box 14: Date of the current illness, injury, or onset
- Box 17 and 17B: Referring physician’s name and NPI number
- Box 21: ICD-10 diagnosis codes
- Box 23: Prior authorization number (if required)
- Box 24D: CPT procedure codes for the services provided
- Box 24F: Charges for each service line
Missing or mismatched information in any of these fields is one of the top reasons claims get kicked back. Double-check that the diagnosis codes support the procedure codes, that the referring provider’s information is current, and that authorization numbers are included when the payer requires them.
Handle Denials and Appeals
Even well-run practices deal with claim denials. Most fall into two broad categories: technical errors (missing information, wrong codes, expired authorizations) and medical necessity disputes (the insurer doesn’t agree the treatment was needed). The most common specific reasons include missing or incorrect claim information, unmet deductibles, out-of-network status, lack of prior authorization, and services deemed not medically necessary.
When a claim is denied, start by reading the explanation of benefits (EOB) carefully. The remark codes tell you exactly why the claim was rejected. For technical errors like a missing modifier or wrong date of birth, correct the information and resubmit promptly. These are usually straightforward fixes, but you may need to follow up to confirm the corrected claim was actually processed.
Medical necessity denials require a more involved appeal. Ask the referring physician to write a letter confirming why the treatment was needed. Include your clinical documentation showing the patient’s functional limitations, the skilled interventions provided, and the measurable progress (or the clinical reasoning for continued care if progress is slow). Supporting evidence from peer-reviewed literature showing the treatment is standard practice for the diagnosis strengthens the appeal. Most insurers have a formal appeals process with specific deadlines, typically 30 to 180 days from the denial date depending on the payer.
Track Your Revenue Cycle
The billing process doesn’t end when you submit a claim. Track every claim from submission through payment, and monitor your accounts receivable aging regularly. Claims sitting unpaid beyond 30 to 45 days need attention. Either the payer hasn’t processed them, or something was rejected without your knowledge.
Key metrics to watch include your clean claim rate (the percentage of claims accepted on first submission), your average days in accounts receivable, and your denial rate by reason code. If you see the same denial reason appearing repeatedly, that points to a systemic issue in your workflow, whether it’s inconsistent authorization checks, documentation gaps, or coding errors. Fixing the root cause is always more efficient than appealing the same type of denial over and over.