How to work claim denials: a step-by-step guide

What does it mean to work a claim denial?

Working a denial means taking an adjudicated “no” from a payer and turning it into one of four outcomes: paid on a corrected claim, paid on appeal, corrected through a reopening, or written off with a reason you can defend. Each denial gets a cause, an owner, a route and a date. Anything less is logging, not working.

Separate denials from rejections first. A rejection stops at the clearinghouse or the payer’s front end; the claim never adjudicated, there is no remittance line, and the timely filing clock is still running. A denial has a remittance line with a reason code, an appeal path and a deadline. Medicare’s manual calls a claim with incomplete, missing or invalid required information an unprocessable claim and says it must be corrected or resubmitted; when such a claim is returned at the front end, no remittance advice is issued at all⁵. Those go back through submission, not through the process below.

The rest of this guide is the denial process in seven steps: read, classify, choose the route, meet the deadline, log, measure, prevent.

Step 1: how do you read the denial on the 835?

Read the group code, the reason code and the remark code together, at the line level, before you form an opinion about the claim. The remittance tells you what the payer did; the codes tell you why.

Medicare’s remittance, electronic 835 or paper, reports the final adjudication for every claim and line with the reason and value of each adjustment; the CARC gives the overall explanation and RARCs add more specific detail⁴. On the 835 each adjustment has three parts:

• The group code assigns responsibility for the adjustment amount¹. X12’s current list has four: CO, OA, PI and PR³. CO means the provider absorbs the amount under contract, PR moves it to the patient, and OA and PI are neither.
• The claim adjustment reason code explains why the payment on the line differs from the charge¹.
• The remark code gives more detail about the adjustment the CARC reported, or passes on information about how the remittance was processed; informational remarks begin with “Alert:”².

The same CARC means different things with different remarks. On its own, CARC 16 only tells you that something on the claim was missing or wrong¹, which is a shrug. The remark narrows it. Paired with M51, the problem is the procedure code itself: absent, incomplete or not a valid code². Paired with MA130, the payer could not process the claim at all, so there is nothing to appeal². Paired with MA04, a secondary payer could not act because the claim did not show who the primary was or what it paid². Three different fixes, one CARC. The CO-16 page walks each pairing.

Two habits save hours. Read every line on the claim, not only the one that denied; a payer that pays one line and denies another has told you the claim adjudicated and eligibility was fine. And keep the X12 lists open; they are the only official definitions, and the lists change.

Step 2: how do you classify the root cause?

Assign one root cause per denial from a fixed list, based on the code pair plus the claim history, and name the person who can fix that cause. The code tells you what the payer saw; the cause tells you where the process broke.

The categories do real work in the prevention step. A month of denials sorted by cause tells you whether the problem is at the front desk, in the coding, or at the payer. Sorted by code alone it tells you less, because CARC 16 covers everything from a missing NDC to a wrong taxonomy code.

For bundling denials, check the NCCI edits before you argue. CMS publishes procedure-to-procedure edits to prevent improper payment when incorrect code combinations are reported, and medically unlikely edits to catch incorrect units of service; both files are updated quarterly¹⁶. If the pair is in the table and the note does not support an exception, the denial is correct.

For COB denials, confirm who is primary. When a patient has Medicare and other coverage, coordination of benefits rules decide which pays first, and CMS takes action to recover Medicare payments made when another payer should have paid first¹⁷. Fixing the order with the patient’s plans is slower than resending the claim, and it is the only fix that lasts.

Step 3: corrected claim, reopening, appeal or write-off?

Choose the route by asking one question: did the payer decide something, or did it fail to receive something? Missing or wrong data means a corrected claim or a reopening. A decision you disagree with means an appeal. A correct denial with no recoverable path means a write-off with a recorded reason.

Corrected claims

A corrected claim replaces the original in the payer’s system. Use the payer’s process: a replacement claim carrying the payer’s original claim number where the payer’s manual calls for one, or a fresh claim where the payer treated the original as unprocessable and never kept it. Appealing a data error wastes the appeal window and may come back unread.

Reopenings (Medicare)

Medicare separates minor errors from appeals. CMS defines clerical errors to include mathematical or computational mistakes, transposed procedure or diagnosis codes, inaccurate data entry, misapplication of a fee schedule, computer errors, claims wrongly denied as duplicates, and incorrect data items such as provider number, modifier or date of service, and requires that they be processed as reopenings rather than appeals⁶. A party may request a reopening within one year of the initial determination for any reason, or within four years for good cause⁶. The limit is on form and content: a reopening cannot add items or services that were not billed⁶.

Appeals

An appeal asks the payer to review its decision with evidence. For commercial payers the levels, forms, addresses and the date each deadline counts from are in the provider manual. For Medicare the five levels and deadlines are fixed by regulation, which is why the table in the next step is worth knowing even when Medicare is a small share of your mix.

Write-offs

A write-off is a decision, not a default. Record the cause (timely filing, non-covered, bundled, below the cost of appeal) so it shows in the prevention data. Write-offs with no cause are where a practice’s real denial rate hides.

Step 4: what are the deadlines?

Every route has a clock, and the clock does not wait for someone to read the remittance. Medicare’s first appeal deadline runs from receipt of the initial determination⁷, which reaches you on the remittance. Put the deadline in the log on the day the denial arrives.

For Medicare Part B, the appeal path runs through five levels:

Three details from the CMS pages matter in practice. Medicare presumes you received the remittance five days after the notice date unless there is evidence otherwise, so the 120 days effectively start five days after the 835 date¹². A redetermination request must carry the beneficiary’s name and Medicare number, the specific services and dates, the name of the party or representative, and an explanation of why you disagree⁷. And documentation not submitted by the reconsideration level may be excluded at later levels unless you show good cause⁸, so the records go in at level one or two, not at the hearing.

Timely filing has its own clock. Medicare requires claims within 12 months, or one calendar year, of the date of service, counted from the line item “From” date on professional claims⁵. Federal Medicaid rules require states to make providers submit claims within 12 months of the date of service¹³. A corrected claim that goes out after that window can trade a fixable CARC 16 for an unfixable CARC 29. If the original was filed late in the window, send the correction the same day you read the remark code. The Medicare timely filing page covers the exceptions.

Commercial and Medicaid MCO deadlines vary by contract and by state and can be shorter than Medicare’s. Treat the payer’s provider manual as the source, and record the deadline per payer in the log.

Step 5: what goes in the denial log?

A denial log is one row per denied line (or per claim, where the payer denies whole), with enough columns to answer three questions on any day: what is open, what is due this week, and what keeps recurring. A spreadsheet works; a practice management system’s work queue works better if it holds the same fields.

Work the log in two sorts. By deadline, so nothing expires. Then by dollars within the same deadline week, so the valuable ones go first. A denial that has been “in progress” for a month with no next action date is not in progress.

Step 6: how do you measure the work?

Report denials weekly in counts and dollars, by payer and by root cause, alongside the overturn rate and the write-offs. Use a published formula for the denial rate so the trend means something.

Two formulas are in common use and they differ. HFMA’s MAP Key divides the total number of claims denied by the total number of claims remitted¹⁵. AAFP’s version divides the dollar amount of claims denied by the dollar amount of claims submitted in the period¹⁴. AAFP puts the industry average at 5 to 10 percent and calls a rate below 5 percent more desirable¹⁴. Report both: a practice with a low count rate and a high dollar rate has a high-value service line in trouble.

Track the share of denials that were preventable (eligibility, authorization, registration, timely filing) separately from the ones that needed an argument (medical necessity, payer policy). The preventable share is the number the front end can move. The denial revenue leak estimator turns monthly volume and overturn rate into a dollar figure you can put in front of the practice owner.

Step 7: how do you stop the same denial coming back?

Once a month, take the top denial causes by dollars and turn each into a front-end change with an owner and a check date. That loop, more than any appeal skill, is what lowers the rate.

The fix depends on the cause:

• Registration and data errors become scrubber rules: one rule per remark code you have seen in the last year, so the field is checked before the claim leaves.
• Eligibility denials become a check on every visit, not only new patients, with the plan name compared to the payer the claim will go to.
• Authorization denials become an auth field the biller can see at charge entry, with the unit count and date range, and a hold on claims that lack it.
• Bundling denials become a coder review of the NCCI pair before the claim, timed to the quarterly edit update¹⁶.
• COB denials become a question at check-in about other coverage and a hold on secondary claims until the primary remittance is posted.
• Timely filing denials become a daily rejection report with an owner, because a rejection that nobody resends turns into a late claim.

Close the loop by watching the cause disappear from the report. If it does not, the fix did not land, and the next monthly review starts there.

When should you hand denials to a billing team?

Hand them over when the log is full and the deadlines are passing, or when the people who could work denials are the same people answering the phones. A remote denial management team reads every 835, logs each denial with cause, owner and deadline, sends corrections and appeals through the payer’s channel, and raises the front-end fix when a cause repeats. Remitwright works this way, with a dedicated biller per client, inside the client’s own system, and a weekly report by payer, cause and dollar. The work is remote; the clinical judgment on medical necessity appeals stays with your clinicians, who get the file prepared for them.

Keep the decision honest. Denials that are correct should be written off, not appealed. Denials worth less than the cost of appealing should be tracked as a cause and fixed at the front end. A team that appeals everything is building a bigger log, not a smaller one.