Accident evidence and claim documents on desk

Why Accident Claims Get Denied: 12 Reasons and Fixes

Byryan@coautoinjury.com

Most accident claims are denied for one of two reasons: the loss falls outside what the policy actually covers, or the paperwork is wrong, late, or missing. Research confirms that denial patterns cluster around contractual exclusions and administrative failures, not some elaborate insurer conspiracy. That distinction matters because it tells you exactly where to push back.

If your claim was just denied, do these five things before anything else:

  • Get the denial in writing. Call the insurer and request a formal denial letter that cites the specific policy language or reason code used.
  • Note every deadline. The letter will state your appeal window. Missing it can forfeit your right to appeal entirely.
  • Preserve all evidence. Photos, medical records, repair estimates, receipts, police reports — gather them now, before anything gets lost or overwritten.
  • Request the insurer’s appeal instructions in writing. They are legally required to provide them.
  • Contact Stubbornattorney if the denial involves significant damages, disputed fault, or a bad-faith pattern. Early legal review costs nothing on a contingency basis and can change the outcome.

Pro Tip: When an adjuster calls after a denial, do not volunteer explanations or apologize for anything. Say you are reviewing the denial letter and will respond through the formal appeal process. Anything you say can be used to support the insurer’s position.

Table of Contents

The most common reasons accident claims get denied

Before diving into the details, here is the short list. Find your situation, then go to the detailed section below.

  • Missed filing or notice deadline
  • Policy lapsed, not active on the date of loss, or the specific peril is excluded
  • Disputed fault or causation (the adjuster says the injury wasn’t caused by the accident)
  • Delayed, inconsistent, or missing medical treatment records
  • Pre-existing condition or aggravation dispute
  • Incorrect or incomplete claim information (wrong codes, dates, member IDs)
  • Policy limits exhausted or uninsured/underinsured motorist (UM/UIM) gap
  • Alleged fraud or material misrepresentation
  • Duplicate submission or coordination-of-benefits error
  • Prior authorization or medical necessity denial (health claims)

Detailed breakdown: what each denial reason means and how to fight it

1. Missed filing or notice deadline

Every policy has a “timely notice” clause. For auto claims, that window can be as short as 24 hours for hit-and-run incidents requiring UM coverage. Workers’ compensation claims in Colorado typically require notice to the employer within four days of the injury and a formal claim within two years. Health claims often carry a 90-day or 180-day timely-filing window from the date of service.

If you missed a deadline, request a late-filing exception in writing. Explain the reason (hospitalization, incapacity, lack of knowledge of the deadline) and attach supporting documentation. If the insurer refuses, file a complaint with your state insurance regulator. Colorado’s Division of Insurance handles these complaints and can compel a response.

Evidence to collect: hospital admission records proving incapacity, any written communication showing you notified the insurer as soon as reasonably possible, the accident injury reporting timeline for your claim type.

2. Policy lapsed or the loss is excluded

A lapsed policy is the clearest denial, but it is worth verifying the exact date coverage ended. Insurers sometimes process cancellations incorrectly. Pull your payment records, the cancellation notice, and the policy’s effective dates. If coverage was active on the date of loss, that is a straightforward dispute.

Exclusions are trickier. Common ones include intentional acts, racing, using a personal vehicle for commercial purposes without a rider, and injuries sustained while committing a crime. Read the exclusion language carefully: exclusions must be specific and unambiguous to hold up. Vague exclusion language often fails on appeal or in court.

For auto claims, check whether UM/UIM coverage applies even when the at-fault driver’s policy is the one that denied or is insufficient. Many Colorado drivers carry UM/UIM without realizing it fills exactly this gap.

3. Disputed fault or causation

This is the most contested category in personal injury claims. An adjuster may concede the accident happened but argue your injury predates it, was caused by something else, or is exaggerated. Below that threshold, your recovery is reduced by your percentage of fault.

The role of negligence in your claim is where police reports, witness statements, and medical causation notes become critical. A treating physician’s note linking the injury onset to the accident date is often the single most powerful document in a causation dispute. Get it in writing, specifically worded.

Evidence to collect: police report, scene photos, witness contact information, emergency room records from the date of the accident, and a causation letter from your treating physician. Gathering accident evidence immediately after a crash significantly reduces the insurer’s ability to manufacture a causation dispute later.

Hands photographing skid marks and debris

4. Delayed, inconsistent, or missing medical treatment

Gaps in treatment are one of the most common reasons personal injury claims fail. Adjusters interpret a two-week gap between the accident and your first doctor visit as evidence the injury wasn’t serious, or wasn’t caused by the accident. A gap of a month or more can effectively sink a soft-tissue claim.

Consistency matters too. If you attended three physical therapy sessions and then stopped, the insurer will argue you recovered. Document every appointment, every cancellation (and why), and every symptom progression. Ask your treating clinician to note in the chart that ongoing symptoms are consistent with the mechanism of injury.

Therapist adjusting wrist brace on treatment table

Pro Tip: If cost or transportation prevented you from keeping appointments, document that in writing now. A note from your doctor acknowledging the barrier is far better than silence.

5. Pre-existing condition or aggravation dispute

Under the ACA’s pre-existing condition rules, marketplace health insurers cannot deny coverage based on a pre-existing condition. But that protection does not extend to clinical denials for medical necessity or prior authorization, and it does not apply to auto liability or workers’ comp claims at all.

In personal injury cases, the “eggshell plaintiff” doctrine holds that a defendant takes the victim as they find them. A pre-existing back condition does not eliminate your right to recover for the aggravation caused by the accident. The key is documenting the baseline before the accident and the measurable worsening after it. Request your pre-accident medical records and ask your physician to write a comparative assessment.

6. Incorrect or incomplete claim information

Wrong member ID, transposed date of service, missing CPT modifier, incorrect diagnosis code — these are administrative errors that are fast to fix once identified. The denial reason code on the Explanation of Benefits (EOB) will tell you exactly what went wrong. Correct the error and resubmit as a corrected claim, not a duplicate.

For auto and personal injury claims, the equivalent errors include wrong vehicle identification numbers, incorrect accident dates, or missing supporting documents. Call the insurer’s claims line, confirm what is missing, and resubmit with a cover letter noting the correction.

7. Policy limits exhausted or UM/UIM gap

When the at-fault driver’s liability limits are exhausted, your own uninsured/underinsured motorist coverage becomes the next line of recovery. Many claimants do not realize they have UM/UIM coverage or do not know how to invoke it. Pull your own declarations page and look for UM/UIM coverage amounts.

If your own limits are also insufficient for the damages, a personal injury attorney can identify additional sources of recovery: umbrella policies, employer liability if the at-fault driver was working, or third-party premises liability.

8. Alleged fraud or material misrepresentation

Fraud allegations are serious and require a careful response. Do not make additional statements to the insurer without understanding what triggered the allegation. Request the insurer’s factual basis in writing. Common triggers include inconsistencies between your recorded statement and the police report, prior claims history, or surveillance footage.

If the allegation is based on a misunderstanding or a clerical error, correct it with documentation. If it is based on something more substantive, involve an attorney before responding further.

9. Duplicate submission or coordination-of-benefits error

When you have more than one insurance policy (for example, health insurance through your employer and through a spouse’s employer), the coordination-of-benefits rules determine which pays first. Submitting to both simultaneously without following COB protocols triggers a denial from the secondary payer. Contact both insurers, establish which is primary, and resubmit to the secondary with the primary’s EOB attached.

10. Prior authorization or medical necessity denial

Industry analysis shows that prior authorization and medical necessity denials are among the most common in health claims, and that many are overturned on internal appeal when additional clinical documentation is provided. The appeal here is clinical, not administrative: your provider needs to submit peer-reviewed support for the treatment, the treating physician’s notes explaining why the treatment is necessary, and any relevant clinical guidelines.

Medical billing denial codes: what they mean and how to fix them

Claim denial reason codes are standardized identifiers that tell you exactly why a health claim was rejected. RevCycleManagement documents the most common CO- and OA-series codes and the corrective actions for each.

Code Plain-English Meaning Immediate Fix
CO-15 Missing or invalid authorization number Obtain the prior authorization retroactively if possible; resubmit with the correct auth number
CO-16 Missing or incorrect claim information Identify the specific field flagged on the EOB; correct and resubmit as a corrected claim
CO-18 Duplicate claim submission Confirm the original was processed; if not, resubmit with a note that this is not a duplicate
CO-29 Timely filing limit exceeded Submit proof of timely filing (original submission date, system logs); request a timely-filing exception
CO-50 Medical necessity not established Have the treating physician submit clinical notes, diagnosis rationale, and peer-reviewed support
OA-18 Claim submitted to the wrong payer Identify the correct primary payer; resubmit to the right insurer with COB documentation

Steps for patients working with billing staff:

  • Ask for the EOB the day the denial arrives, not weeks later.
  • Confirm whether the denial is administrative (codes CO-15, CO-16, CO-18, CO-29, OA-18) or clinical (CO-50). Administrative denials are usually fixed with a corrected resubmission. Clinical denials require a formal appeal with supporting documentation.
  • For CO-50 denials, ask your provider to write a letter of medical necessity and attach relevant clinical guidelines.
  • If internal appeal fails, request an external independent review. Most states, including Colorado, offer an Independent Medical Review process for health claim disputes.
  • If the carrier violated statutory response timelines, file a complaint with the Colorado Division of Insurance.

How to appeal a denied accident claim, step by step

Most denied claims are appealable. KFF’s analysis of ACA marketplace plans found that few denied claims are successfully appealed by consumers acting alone, which underscores the value of knowing exactly what to submit and when.

Step 1: Read the denial letter in full. Note the specific reason cited, the policy section referenced, and the appeal deadline. Most internal appeal windows run 30 to 180 days from the denial date, depending on the claim type and state law.

Step 2: Request the insurer’s complete claim file. You are entitled to the documents the insurer relied on. This often reveals the adjuster’s notes, surveillance records, or medical reviews that drove the denial.

Step 3: Build your appeal package. Include:

  • A cover letter with a factual chronology of the accident, treatment, and claim submission
  • Copies of all medical records, repair estimates, and receipts
  • Witness statements and the police report
  • The specific policy language you believe covers the loss
  • Any expert reports, physician causation letters, or independent assessments

Step 4: Submit the internal appeal in writing, with proof of delivery. Certified mail or a carrier’s secure portal with a confirmation timestamp both work.

Step 5: If the internal appeal is denied, request an external review. For health claims, Colorado law provides access to an independent external review. For auto and personal injury claims, the next step is typically a complaint to the Colorado Division of Insurance or a demand letter from an attorney.

Step 6: File a state regulator complaint if the carrier violated timelines or acted in bad faith. Regulatory complaints often succeed when the denial is procedurally thin or the insurer failed to respond within statutory deadlines. The Colorado Division of Insurance complaint process is available online and costs nothing to file.

For a full breakdown of the insurer’s timeline obligations, the insurance claim workflow guide walks through what to expect at each stage.

When should you hire an attorney?

DIY appeals work for straightforward administrative errors. They are much less reliable when the stakes are high or the dispute is substantive. Hire an attorney when:

  • Your damages exceed your policy limits or the at-fault driver is underinsured.
  • The insurer disputes causation and you need expert medical or accident reconstruction testimony.
  • The statute of limitations is approaching. In Colorado, personal injury claims generally must be filed within three years of the accident date. Missing that deadline ends the case permanently.
  • The insurer is acting in bad faith: unreasonable delays, lowball offers without explanation, failure to investigate, or misrepresenting policy terms.
  • Workers’ compensation claims involve disputed injury classifications or permanent impairment ratings.
  • The denial involves a coverage exclusion that you believe is ambiguous or improperly applied.

A personal injury attorney will file a formal demand, handle all adjuster communications, coordinate medical and expert evidence, and file suit if the insurer refuses a fair resolution. At Stubbornattorney, representation is on a contingency basis: no fee unless there is a monetary recovery. That structure means the firm’s incentive is exactly aligned with yours.

Questions to ask during a free consultation:

  • What is the likely value range of my claim?
  • Do you see any bad-faith indicators in the denial letter?
  • What evidence do I still need to collect?
  • What is the statute of limitations deadline for my specific claim?
  • What percentage do you charge, and what costs are reimbursed from the settlement?

Legal representation in car accident claims changes the dynamic with adjusters in ways that a self-represented claimant rarely can replicate.

What I’ve learned from the other side of the desk

The thing most people do not realize about insurance denials is how mechanical the process is. Adjusters work from checklists. A denial is often not a judgment about your honesty or the severity of your injury. It is a flag that a required field is missing, a deadline passed, or the claim does not fit the adjuster’s initial read of the policy.

That is actually useful information. It means most denials are fixable, if you know what the insurer is looking for and you move quickly. The problem is that injured people are dealing with pain, medical appointments, and financial stress at the exact moment they need to be building a paper record. That gap is where claims die.

What I look for when a denied claim comes to my desk is the insurer’s own file. Adjusters take notes. Those notes often reveal whether the denial was a genuine coverage question or a procedural shortcut. When I see a denial letter that cites a vague exclusion without quoting the specific policy language, that is a signal the insurer is not confident in its position. When I see a denial based on “failure to cooperate” but the claimant has documentation of every communication, that is a bad-faith indicator worth pursuing.

The other pattern I see consistently: people wait too long. They assume the denial is final, or they spend weeks going back and forth with a customer service line that has no authority to reverse anything. The formal appeal process, the regulator complaint, the demand letter from counsel — those are the levers that actually move insurers. The phone call to a general claims line is not.

Stubbornattorney can fight your denied claim for you

A denied claim is not the end of the road, but the window to reverse it is shorter than most people think. Stubbornattorney, the brand home of Malnar Injury Law, represents injured Coloradans on a contingency basis: you pay nothing unless the firm recovers compensation for you. Ryan Malnar spent years as a federal claims adjudicator before becoming a personal injury attorney, which means he knows exactly how insurers evaluate and deny claims from the inside out.

The firm handles free consultations for denied accident claims, disputed causation cases, and bad-faith insurance conduct across Colorado. Schedule a free case evaluation to get a direct assessment of your denial and your options. For a full overview of the firm’s personal injury services in Colorado Springs, including auto, truck, motorcycle, and slip-and-fall cases, visit the practice area page.

Sources

This article is general information, not a substitute for advice from a qualified lawyer. Consult a qualified legal professional about your own circumstances before acting on anything here.

FAQ

What are the most common reasons insurance claims are denied?

The two largest categories are coverage exclusions (the loss is not covered under the policy) and administrative failures (missed deadlines, coding errors, missing documents). Law review analysis confirms that most denials cluster around these two categories rather than outright bad faith.

Can a denied accident claim be appealed?

Yes. Every insurer is required to provide appeal instructions with the denial letter. Internal appeals must typically be filed within 30 to 180 days of the denial. If the internal appeal fails, external review and state regulator complaints are available next steps.

What is the most common reason medical claims are denied?

Prior authorization failures and medical necessity disputes are among the most frequent, followed by coding errors and timely-filing violations. Industry analysis shows that many medical necessity denials are overturned on internal appeal when the treating provider submits additional clinical documentation.

How do I know which denial code applies to my medical claim?

The Explanation of Benefits (EOB) from your insurer will list the denial reason code. CO-series codes indicate contractual adjustments; OA-series codes indicate other adjustments. The RevCycleManagement denial code guide explains what each code means and the specific corrective action required.

When should I hire a lawyer for a denied accident claim?

Hire an attorney when the damages are significant, the insurer disputes causation, the statute of limitations is approaching, or the denial shows signs of bad faith. Stubbornattorney offers free consultations and works on contingency, so there is no upfront cost to getting a professional assessment of your denied claim.

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