Why was my insurance claim denied?
Your denial letter has the answer — here's how to read it.
Every denial letter is required to tell you why. This guide labels the letter field by field, and breaks down the most common reason categories so you know what you're dealing with.
See a denial letter, labeled ↓Your denial letter, labeled
Illustrative example — actual letters vary by insurer, but most include these same core elements.
Illustrative example — actual letters vary by insurer.
Service & date
Confirms which specific claim this letter is about.
Denial reason code
A short code behind the decision — the starting point for understanding what actually happened.
Plain-language explanation
Required to be understandable, not just a code — read this closely.
Plan provision cited
The specific section of your plan the insurer says applies.
Appeal deadline
A hard deadline — missing it can forfeit your right to appeal.
How to appeal
The specific process and address or portal for your plan.
External review rights
Your right to have an independent third party review the decision, after internal appeals.
Three categories of denial reasons
Your reason code generally falls into one of these — and it shapes how promising an appeal is likely to be.
Technical or clerical
- Missing or incomplete information
- Coding errors
- Eligibility or enrollment issues
- Filed after the deadline
Medical judgment
- "Not medically necessary"
- Considered experimental or investigational
- Wrong level of care (e.g., inpatient vs. outpatient)
Plan design
- Service excluded from your plan
- Prior authorization missing
- Provider out-of-network
- Annual benefit limit reached
Not sure which category applies?
See the difference between an excluded service and a denied claim →
The clock is ticking
Appeal deadlines are real
Most plans give you a limited window — often around 180 days, though this varies — to file an internal appeal. Missing it can mean losing your right to challenge the decision entirely. If you're planning to appeal, start sooner rather than later.
What to check on your denial letter
- What's the exact denial reason code?
- Does the explanation match what actually happened?
- What's the appeal deadline?
- Is this administrative, clinical, or coverage-related?
- What documentation would strengthen an appeal?
- Do I have external review rights if the appeal fails?
In Canada? Formal denial letters mostly apply to a different layer of coverage.
Jump to the Canadian guide ↓Formal denial letters are more of a private-plan concept
For most core medical and hospital care, providers bill your provincial plan directly, so there's often no patient-facing denial letter for routine care. That changes in a couple of situations.
Specific approvals can still be denied
Certain procedures, out-of-province care, or pre-approval requests can receive a formal denial with provincial appeal rights — rules vary by province and territory.
Denial letters work much like the U.S.
For drug, dental, vision, and paramedical claims through a private plan, denial letters and appeal rights are common — the same "read the reason code" approach applies.
Common questions about denials
What if I don't understand my denial reason code?
Call the customer service number on your denial letter or insurance card and ask them to explain it in plain language — they're required to be able to do this.
Can more than one reason apply to the same denial?
Yes — a single claim can be denied for multiple reasons at once, which is why reading the full explanation, not just the code, matters.
Does a denial mean the care wasn't appropriate?
Not necessarily — many denials are administrative or based on incomplete documentation rather than a judgment about whether the care was medically appropriate.
What's the difference between an internal appeal and external review?
An internal appeal is reviewed by your insurer. External review is generally an independent third party, available after internal appeals are exhausted.
Understand the reason. Then act on it.
The right response depends entirely on which kind of denial you're looking at.