What Is Accounts Receivable (AR) in Medical Billing? Process, Days in AR, and Fixes

You delivered the care. The claim went out. Sixty days later, the payment is still missing. That gap is your accounts receivable (AR) in medical billing, and it decides whether payroll clears on time. This guide explains what AR is, how the AR process works, which numbers to watch, and which 2026 changes put your cash flow at risk. Each section opens with a direct answer you can act on in minutes.

What Is Accounts Receivable (AR) in Medical Billing?

AR in medical billing is the money owed to your practice for care already delivered. It sits in two buckets:

• Insurance AR: claims pending with Medicare, Medicaid, and commercial payers
• Patient AR: copays, deductibles, coinsurance, and self-pay balances

A balance enters AR when the claim is submitted and leaves when payment posts or an approved adjustment clears it. Insurance AR needs appeals and documentation. Patient AR needs clear statements and payment options. AR looks like an asset on paper and behaves like a liability the longer it ages.

How Does the AR Process Work in Medical Billing?

The AR process runs from patient registration to a zero balance in eight steps:

1. Eligibility verification and prior authorization before the visit
2. Charge capture and medical coding with accurate ICD-10-CM, CPT, and HCPCS codes
3. Claim scrubbing and claim submission, ideally within 72 hours of service.
4. Payer adjudication: the payer pays, denies, or pends the claim
5. Payment posting from the ERA or EOB, with adjustment codes read correctly
6. AR follow-up on unpaid claims through aging reports and payer portals
7. Denial management and appeals for rejected or underpaid claims
8. Patient billing and account closeout: statements, payment plans, and write-off review

Industry research puts potentially avoidable denials near 86 percent. Steps 1 to 3 hold the biggest savings. A tight revenue cycle management workflow protects all eight.

What Is a Good Days in AR Number in 2026?

Aim for days in AR under 40. The AAFP treats 50 days as the ceiling and 30 to 40 days as preferred. 

Days in AR = total AR ÷ average daily charges. With $450,000 in AR and $10,000 in daily charges, your days in AR is 45.

One number hides problems. Track four together:

• AR over 90 days: many teams aim to keep it below 10 to 15 percent of total AR.
• Denial rate: HFMA treats below 5 percent as optimal.
• Net collection rate and clean claim rate
• Net days in AR: excludes balances older than about 120 days that are unlikely to be collected.

Run days in AR by payer, not only for the whole practice. One slow payer can hide behind a healthy average.

Why Do Claims Age in AR & What Should You Do at Each Stage?

Claims age from front-end errors, slow follow-up, and unworked denials. Match the action to the age:

Work claims by dollar value and deadline, not by claim order. A $3,000 claim with 20 days left before timely filing beats ten $80 claims.

Which ICD-10, CPT, and HCPCS Codes and Modifiers Affect AR Most?

Code mismatches and thin documentation create the denials that age in AR. Watch these:

• ICD-10-CM: E11.9 and E11.65 (type 2 diabetes without complications and with hyperglycemia), I10 (hypertension), Z00.00 and Z00.01 (adult exam without and with abnormal findings). Specific diagnoses support medical necessity. Z59.86 (financial insecurity) flags patients who need payment plans. It documents hardship and does not change payer payment.
• CPT: 99213 and 99214 (established patient visits), 99490 (chronic care management), 99457 (remote monitoring management). Time-based codes need documented minutes.
• HCPCS: G2211 (visit complexity add-on), G0463 (hospital outpatient clinic visit), A4239 and E2103 (CGM supply allowance and receiver). DME claims age fast without documentation.
• Modifiers: 25 (separate E/M on the same day), 59 (distinct service, only with documentation), GA (ABN on file), KX (policy requirements met).
• Adjustment codes: CO-29 (timely filing), CO-16 (missing information), CO-50 (medical necessity). CO balances generally cannot be billed to the patient. PR-1, PR-2, and PR-3 (deductible, coinsurance, copay) can. Posting them wrong creates false patient AR.

Verify every code against the CDC ICD-10-CM files, the AMA CPT resources, and payer policy. Our medical coding services team reviews code pairs before claims leave. Our care management programs cover CCM and RPM services.

What Changes in 2026 Put AR at Risk?

Four shifts hit collections this fall:

• FY 2027 ICD-10-CM starts October 1, 2026, with 190 new codes, 30 deletions, and four revisions. New laterality codes such as M67.A01 (plantar fasciitis, right foot) and M67.A02 (left foot) arrive. Claims for dates of service on or after that day with retired codes will reject. Update your EHR code library and superbills now at acdismyzhealth.
• Prior authorization clocks: beginning January 1, 2026, affected payers must decide within 72 hours for urgent and seven calendar days for non-urgent requests, and must give a specific denial reason. Note these deadlines in your follow-up logs. 
• Denial pressure: 41 percent of providers report denial rates above 10 percent. A Health Affairs study of 2019 claims found Medicare Advantage plans denied about 17 percent of initial claims, and 57 percent of denials were later overturned. Appeal before you write off. 
• Three clocks per claim: the payer’s payment clock, the timely-filing clock, and the appeal clock. Medicare requires filing within 12 months of the date of service (see the CMS manual), and a timely-filing denial carries no appeal rights. Medicare’s redetermination appeal window is 120 days from the initial determination. Commercial windows vary by contract. 

How Can You Reduce AR Days Without Hiring More Staff?

Fix the front end, automate status checks, and hand aged accounts to specialists.

• Verify eligibility before every visit and collect copays at check-in
• Work denials within one week of receipt
• Review aging reports weekly by payer and bucket
• Send patient statements with payment links and plans
• Audit yearly for underpayments and coding gaps

P3Care supports each step. Our accounts receivable management team works aged claims. Denial management services find root causes. P3Merge, our billing software, supports daily claim tracking. Credentialing services close enrollment gaps that trigger denials. A medical billing audit finds hidden revenue leakage. Practices in Texas, California, and Nevada get state-aware billing support.

Conclusion

AR is the pulse of your practice. Keep days in AR under 40, work claims by age and dollar value, prepare for the October 1 code change, and track all three clocks. Small front-end fixes save the most money later.

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FAQs

What does AR mean in a medical billing job?

An AR analyst works the aging report, calls payers, checks claim status, and reworks denied claims until the balance is paid or adjusted.

Is AR follow-up the same as denial management?

No. AR follow-up chases unpaid and pending claims. Denial management finds why claims failed, files appeals, and stops the same denial from returning.

When is it safe to write off an AR balance?

Write off only after the final appeal, secondary billing, and patient responsibility steps are complete and documented under a written policy. Routine waivers of copays or deductibles can breach payer contracts.

Does outsourcing AR follow-up put patient data at risk?

Not when the vendor signs a business associate agreement and follows HIPAA safeguards. Confirm access controls, audit logs, and breach procedures. See how HIPAA medical billing works at P3Care.

Which reports do AR teams use every day?

The aging report by payer, the denial report, the clearinghouse rejection report, remittance files, and an unbilled claims report. The unbilled report catches charges that never became claims.