Accounts receivable (A/R) aging is simply a breakdown of how long unpaid balances — insurance and patient — have been sitting on a practice's books. The longer a dollar stays outstanding, the less likely it ultimately gets collected, which is why most billing teams organize their A/R into time-based "buckets" and apply a different follow-up tactic to each one rather than treating all outstanding claims the same way. This article walks through that bucket framework, shows the actual calculation behind one of the most commonly referenced A/R metrics, and ends with a practical follow-up checklist.
What A/R Aging Measures, and Why It Matters
An A/R aging report groups every open balance by the number of days since the claim was billed (or, for patient balances, since the statement was generated). Most practice management systems default to four or five buckets — commonly current/0–30, 31–60, 61–90, and 90+ days — though some systems extend further to 120+ or 180+ day ranges. The report matters because it turns a single lump "total A/R" number into a picture of where the money actually is and how urgently each portion needs attention.
Left unmanaged, A/R aging tends to drift in one direction: older. Claims that should have been resolved in 30 days quietly become 60-day claims, then 90-day claims, and the longer a balance sits, the harder it typically becomes to collect — payer timely-filing and appeal windows close, patients move or lose coverage, and staff attention naturally shifts to newer, easier work. A structured aging review is how a billing team keeps that drift from becoming permanent revenue loss.
Why Outstanding Claims Accumulate
Before applying a bucket strategy, it helps to understand the general reasons balances end up aging in the first place. Common causes include:
- Eligibility and registration issues — coverage that had lapsed, an incorrect payer ID, or a plan that requires authorization the claim did not reflect.
- Claim denials that were never reworked or appealed and simply sit as an open balance (see our guides on how to reduce claim denials and denial management best practices).
- Underpayments — the payer processed and paid the claim, but at less than the contracted rate, and the shortfall was never identified or pursued.
- Slow or inconsistent follow-up — no one systematically works claims that haven't been paid in a set number of days, so they simply age on their own schedule.
- Patient-responsibility balances that are never reviewed or escalated into a structured billing and reminder process.
A dedicated accounts receivable management function — whether staffed internally or handled through an outsourced partner — exists specifically to catch these issues on a regular cadence rather than only when a balance has already become old and difficult.
A Bucket-by-Bucket Follow-Up Framework
Rather than working the oldest or largest balances first by instinct, many billing teams assign a distinct, appropriate action to each aging bucket. The logic: a 20-day-old claim and a 100-day-old claim usually have different underlying problems, so they call for different responses.
Current / 0–30 Days
At this stage, most claims are simply moving through the normal payer adjudication cycle. The priority here is confirmation, not aggressive follow-up: verify the claim was actually received and accepted by the payer (not stuck in a clearinghouse rejection), and resolve any front-end eligibility problems immediately so they don't resurface later in the cycle. This is also where payment posting accuracy matters — a payment posted incorrectly, or not posted at all, can make a resolved claim look like it's still outstanding.
31–60 Days
By this point, a claim that hasn't paid or denied is worth a direct status check with the payer. This is the stage for first-line insurance follow-up: confirming the claim is in process, identifying whether additional documentation was requested, and catching early signs of a denial before it ages further.
61–90 Days
Claims in this range typically represent a problem that first-line follow-up didn't resolve — a denial that needs appeal, an underpayment that needs to be identified against the contracted fee schedule, or a payer response that was never received. This is the point to escalate beyond a routine status call: involve a biller or supervisor who can file an appeal, request a reprocessing, or open a payer escalation before timely-filing or appeal deadlines close.
90+ Days
Balances in the 90+ day bucket represent the highest collection risk and deserve the most direct attention — typically a case-by-case review of each claim, confirmation of appeal and timely-filing deadlines, and a decision on whether further pursuit, a secondary appeal, or write-off (per the practice's own financial policy) is appropriate. Because every day of additional age reduces the realistic chance of recovery, many practices specifically track what share of their total A/R sits in this bucket.
Calculating the Percentage of A/R That Is 90+ Days
This is one of the simplest and most commonly referenced A/R metrics, and the formula is a direct ratio:
Percentage of Total A/R in the 90+ Day Bucket = (Dollars Outstanding in the 90+ Day Bucket ÷ Total Outstanding A/R, All Buckets Combined) × 100
For example — using illustrative numbers only, not a benchmark — if a practice's total outstanding A/R across all buckets is $500,000, and $60,000 of that total sits in the 90+ day bucket, the calculation is: $60,000 ÷ $500,000 × 100 = 12%. That figure tells the billing team what portion of all outstanding dollars is at the highest risk of becoming uncollectible, separate from the dollar amount alone.
Prioritizing High-Value Accounts and Escalating with Payers
Not every open claim deserves equal time. Many billing teams sort each aging bucket by dollar value and work the highest-value outstanding accounts first, since a small number of large claims often represents a disproportionate share of total outstanding revenue. Pairing that prioritization with timely payer escalation — requesting a claim reprocessing, filing a formal appeal, or involving a payer's provider-relations contact once a claim has aged past a defined threshold — keeps high-value balances from quietly sliding into the 90+ day bucket unaddressed.
Visibility: Why Regular Reporting Matters
None of the bucket-specific tactics above work without consistent visibility into where every dollar of A/R currently sits. Regular billing reporting and analytics — reviewed weekly or monthly rather than only when a problem surfaces — is what allows a billing team to catch a claim drifting from one bucket to the next before it becomes a 90+ day write-off risk. Aging percentage is just one of several metrics worth tracking on an ongoing basis; see our companion guide on medical billing KPIs every practice should track for the fuller set, including days in A/R, denial rate, and net collection rate.
A Practical A/R Follow-Up Checklist
- Pull an aging report broken out by bucket (current, 31–60, 61–90, 90+) on a consistent schedule, not just when cash flow feels tight.
- Confirm every claim in the current/0–30 bucket was actually received and accepted by the payer, not stuck in a clearinghouse rejection.
- Run direct payer status checks on everything in the 31–60 bucket before it crosses into 61–90.
- Review every 61–90 day claim individually for denial, underpayment, or missing-response causes, and act before timely-filing or appeal deadlines close.
- Sort each bucket by dollar value and prioritize the highest-value accounts for direct follow-up and escalation.
- Calculate the percentage of total A/R in the 90+ day bucket on a recurring basis and track the trend over time rather than a single reading.
- Document a clear internal policy for when an aged balance is escalated, appealed again, or written off.
Frequently Asked Questions
What is a normal number of A/R aging buckets?
Most practice management systems default to four buckets — current/0–30, 31–60, 61–90, and 90+ days — though some extend further into 120+ or 180+ day ranges. The exact bucket structure is a system configuration choice, not a universal standard, so confirm how your own software defines each range.
Is there an ideal percentage of A/R that should be 90+ days?
Published ranges for this exist but vary by specialty, payer mix, and practice size, and are commonly cited without consistent sourcing across billing industry sites. Rather than targeting a specific external number, track your own practice's percentage over time and investigate any upward trend.
Should denied claims be counted in A/R aging?
Yes — a denied claim that has not been appealed, corrected, or written off is still an open balance and should continue aging in your A/R report until it is resolved one way or another. See our guide on how to reduce claim denials for prevention-focused steps.
How often should an aging report be reviewed?
Many practices review it weekly for claims in the earlier buckets and at least monthly for a full aging analysis, though the right cadence depends on claim volume and staffing. The key is consistency — an aging report that is only pulled occasionally tends to let balances drift further before anyone notices.
What is the difference between A/R aging and a denial rate?
A/R aging measures how long unpaid balances have been outstanding, regardless of cause. Denial rate measures what share of claims are rejected by a payer on submission. A denied claim that is never reworked becomes part of your aging A/R, so the two metrics are related but measure different things — see our companion KPI guide for the denial rate formula.
Does outsourcing A/R follow-up help reduce aging?
A dedicated outside team focused specifically on aging A/R, unpaid claims, and underpayments can add consistent follow-up capacity that an internal team stretched across many duties may struggle to maintain, though results depend on claim mix and the specific practice. ChronicSync's accounts receivable management service is built around aging A/R, underpayments, denied claims, and payer follow-up specifically — turning outstanding receivables into collected revenue rather than write-offs.
Sources
- Centers for Medicare & Medicaid Services (CMS.gov) — Federal claims processing and billing guidance.
- Medical Group Management Association (MGMA) — Industry benchmarking data referenced throughout the revenue cycle management field.
- U.S. Department of Health and Human Services (HHS.gov) — Federal health policy and payer-related guidance.