Insurance Appeal Letter Template Plus Six Sample Reconsideration Letters

What is an insurance appeal letter? It is a provider's written request asking a health plan to change a claim decision: it identifies the claim, states the one reason the decision is wrong, asks for a specific remedy and points to the attached proof. Many payers call the first such request a reconsideration and the next one an appeal.

Undeny's Take

The letter is the smallest part of a winning packet. The code on the remittance decides the argument, and the attachments prove it. Three avoidable habits sink most letters: arguing several things at once, never saying what the payer should do, and sending a letter where a corrected claim was the real fix. UnitedHealthcare's own guide says "A corrected claim is not a request for reconsideration," and Medicare treats a wrong modifier as a clerical error for a reopening, not an appeal. So before you open a template, decide which door you are at. Then write one argument, name the remedy in the last paragraph, and quote the payer back to itself: its policy number from the remittance, its contract rate, its own list of acceptable timely filing proof.

Reconsideration, Appeal or Reopening: Name the Request Correctly

Payers do not share a vocabulary. Aetna defines a reconsideration as "a formal review of a previous claim decision" and an appeal as "a written request to change or overturn a previous decision." UnitedHealthcare tells network providers, "First, you must submit a claim reconsideration request," and gives 12 months to complete both steps. Original Medicare flips the words: the first level is a redetermination by the MAC, and "reconsideration" means the second level, decided by an independent contractor.

The practical rule: use the payer's own name for the step in your RE line, because a request filed under the wrong label can be rerouted or delayed. A sample appeal letter for reconsideration and one for a formal appeal use the same skeleton; the appeal version adds the new evidence. UnitedHealthcare's 2026 Administrative Guide is explicit that at the appeal step you should attach "all new supporting materials" and not resend what went with the reconsideration.

Payer	What the first written step is called	Where the deadlines are
Aetna	Reconsideration, then appeal	Aetna provider appeals guide
UnitedHealthcare	Claim reconsideration, then appeal	UHC provider appeals guide
Cigna	Request for Health Care Professional Payment Review	Cigna provider appeals guide
Humana	Claims dispute (participating providers)	Humana provider appeals guide
Anthem	Varies by state, for example a Provider Dispute Resolution Request in California	Anthem provider appeals guide
Kaiser Permanente	Provider Dispute Resolution Request	Kaiser provider appeals guide
UMR	Claim inquiry; formal appeals belong to the member	UMR provider appeals guide
Original Medicare Part B	Redetermination, then QIC reconsideration	Medicare redetermination guide

When a letter is the wrong tool

• You left something off the claim. UnitedHealthcare lists "Additional modifiers, value codes, diagnosis codes or procedure codes omitted from the initial claim" as corrected claim material, sent with frequency code 7 and the original claim number.
• It is a Medicare keying error. CMS Chapter 34 requires clerical errors to be "processed as reopenings rather than appeals," and its list includes "Misapplication of a fee schedule" and "Incorrect data items, such as provider number, use of a modifier or date of service."
• The claim was rejected, not denied. A rejected claim never adjudicated, so there is no decision to appeal; fix and resubmit it inside the filing limit.

The General Insurance Appeal Letter Template

Copy this into your letterhead. It carries every element CMS requires in a written Medicare redetermination request and every item Aetna asks for in a reconsideration, so it works as a base for most payers. Replace each bracketed field; delete any line that does not apply.

[Practice Name]
[Street Address], [City], [State] [ZIP]
Phone: [Phone] · Fax: [Fax]
Billing NPI: [Group NPI] · Tax ID: [Tax ID]

[Date]

[Payer Name]
Attn: [Reconsideration or Provider Appeals Unit]
[Appeal Address or Fax Number Printed on the Denial Letter or EOB]

RE: Request for [reconsideration / appeal] of claim [Claim Number]
Patient: [Patient Name] · Date of birth: [Date of Birth]
Member ID: [Member ID] · Group number: [Group Number]
Date(s) of service: [Date of Service]
Rendering provider: [Rendering Provider Name], NPI [Rendering NPI]
Disputed line(s): CPT [CPT Code] [Modifier], billed [Billed Amount]
Denial: [Group Code]-[Reason Code] [Remark Code], remittance dated [Remittance Date]
Prior reference: [Earlier Reconsideration or Call Reference Number, if any]

Dear [Reconsideration or Appeals] Reviewer:

[Practice Name] requests [reconsideration / a first-level appeal] of the claim identified above, which was [denied / reduced] with reason code [Group Code]-[Reason Code]. We believe this decision is incorrect because [one-sentence reason].

[Two to four sentences of facts: what was done, on what date, by whom, and the single fact that shows the decision is wrong. Name the exhibit that proves each fact.]

[The rule that supports you: the section of our agreement, the plan's policy [Policy Name and Number], the coding guidance, or the filing provision.]

We ask that [Payer Name] [reprocess line [Line Number] at [Contracted Rate] / overturn the denial and pay the claim as billed / apply the corrected claim submitted on [Date]].

Enclosed: (1) [Denial letter or EOB dated [Date]]; (2) [Claim copy]; (3) [Records or proof]; (4) [Other exhibit].

Please contact [Contact Name] at [Phone] or [Email] with any questions.

Sincerely,

[Signature]
[Name], [Title or Credentials]
On behalf of [Practice Name]

How to fill it in without weakening it

• Copy identifiers from the remittance, not your system. The claim number, member ID and dates must match what the payer adjudicated. For Original Medicare, the member ID is the patient's Medicare number, and the request goes to the MAC named on the remittance advice.
• Quote the denial exactly. X12's usage note for CO-50 and CO-97 says to "Refer to the 835 Healthcare Policy Identification Segment (loop 2110 Service Payment Information REF), if present." If your remittance carries a policy number there, put it in your RE block.
• One reason per letter. If two lines were denied for different reasons, send two letters or two clearly separated sections.
• Ask for a remedy a reviewer can execute. "Reprocess line 2 at the contracted rate" gets worked; "please reconsider" gets a form response.

Sample Letters for Six Common Denials

Each sample replaces the body of the general template. Keep the header, RE block and closing from above. All six assume a participating provider disputing its own claim; if the patient filed the claim from a superbill, the member owns the appeal.

Sample 1: Underpayment against the contract rate (CO-45)

X12 defines reason 45 (CO-45) as "Charge exceeds fee schedule/maximum allowable or contracted/legislated fee arrangement." Most CO-45 lines are the normal contractual discount and need no letter. Write this one only when the allowed amount is below the rate in your agreement. Aetna and UnitedHealthcare both treat a reimbursement dispute as a first-step reconsideration; for Original Medicare, "Misapplication of a fee schedule" is a clerical error that goes to a reopening.

RE: Reconsideration, underpayment of claim [Claim Number]
Patient: [Patient Name] · Member ID: [Member ID] · DOS: [Date of Service]
Line(s): CPT [CPT Code], allowed [Allowed Amount], contracted [Contracted Rate]

[Practice Name] is a participating provider under our agreement with [Payer Name], effective [Agreement Effective Date]. The claim above was processed at an allowed amount of [Allowed Amount] for CPT [CPT Code], with the rest of the charge adjusted as CO-45. Under [Fee Schedule Name or Contract Exhibit], the contracted allowable for this code on the date of service is [Contracted Rate].

The difference of [Underpaid Amount] appears to result from [an outdated fee schedule / pricing under the wrong place of service or provider type / a rate not yet loaded for our location at [Service Address]]. We are not disputing the contractual adjustment itself, only the allowable used to calculate it.

Please reprocess line [Line Number] at the contracted rate and issue the additional payment of [Underpaid Amount]. If [Payer Name] believes a different rate applies, please identify the fee schedule and effective date used so we can reconcile our records.

Enclosed: remittance dated [Remittance Date]; the fee schedule page or rate exhibit showing [Contracted Rate]; claim copy.

Sample 2: Bundling with a missing or disputed modifier (CO-97 with 59 or XE, XS, XU)

Reason 97 (CO-97) means "The benefit for this service is included in the payment/allowance for another service/procedure that has already been adjudicated." Check the NCCI edit first: CMS's MLN booklet on modifiers 59 and X{EPSU} explains that a modifier indicator of "0" means the two codes can't be reported together by the same provider for the same patient on the same date, while "1" allows them together only in limited circumstances with a modifier. CMS says to use XE, XP, XS or XU "instead of modifier 59 whenever possible," that "Medical documentation must support the use of the modifier," and not to use 59 or XU "just because the code descriptors of the 2 codes are different." For therapy, CMS's own example is CPT 97140 with 97750: a modifier is appropriate when the two timed services were performed "in distinctly different 15-minute time blocks."

If you simply left the modifier off, send a corrected claim (or, for Original Medicare, request a reopening), and use this letter as the cover note only if the payer asks for one. Use it as a reconsideration when the modifier was on the claim and the line was still bundled. APTA also publishes a 59 modifier appeal template for its members.

RE: Reconsideration, CO-97 bundling of CPT [Column 2 Code] on claim [Claim Number]
Patient: [Patient Name] · Member ID: [Member ID] · DOS: [Date of Service]
Codes: CPT [Column 1 Code] and CPT [Column 2 Code]-[59 / XE / XS / XU]

On [Date of Service], [Rendering Provider Name] performed CPT [Column 1 Code] and CPT [Column 2 Code]. [Payer Name] denied CPT [Column 2 Code] as included in CPT [Column 1 Code] (CO-97). The services were separate and distinct, and the claim [carried / has been corrected to carry] modifier [Modifier] on CPT [Column 2 Code].

The services were distinct because [choose one: they were performed in separate, non-overlapping time blocks, [Start Time] to [End Time] and [Start Time] to [End Time] / they were performed on separate anatomic sites, [Site 1] and [Site 2] / they were performed at separate encounters on the same date / the second service does not overlap the usual components of the first]. The [treatment or procedure note] for the date of service documents this on page [Page Number].

[The code pair carries an NCCI procedure-to-procedure edit with a modifier indicator of 1, which permits a modifier when the services are separate and distinct. / The plan's reimbursement policy [Policy Name and Number] recognizes modifier [Modifier] for this code pair.] We ask that you reprocess CPT [Column 2 Code] for payment.

Enclosed: remittance dated [Remittance Date]; [corrected claim number [Corrected Claim Number] or claim copy]; note for [Date of Service] showing [start and stop times / sites / encounters].

Sample 3: Medical necessity denial (CO-50)

Reason 50 (CO-50) reads "These are non-covered services because this is not deemed a 'medical necessity' by the payer." This is a post-service medical necessity appeal letter, and some payers send it straight to appeal: Aetna lists "Adverse initial claim decisions based on medical necessity" among the decisions that skip reconsideration. If you sent a pre-service letter of medical necessity, attach it, but do not resend it as the appeal; our letter of medical necessity template explains the difference. ASHA's advice applies to every discipline: "reference the coverage policy paragraph that shows how your treatment fits coverage criteria."

RE: Appeal of medical necessity denial, claim [Claim Number]
Patient: [Patient Name] · Member ID: [Member ID] · DOS: [Date of Service]
Service: CPT [CPT Code] · Diagnosis: [ICD-10 Code]
Policy applied: [Policy Name and Number from the denial or remittance]

[Practice Name] appeals the denial of CPT [CPT Code] for [Date of Service], which [Payer Name] adjusted as CO-50 under [Policy Name and Number]. The service met that policy's criteria, and the enclosed record shows it.

[Patient Name] was treated for [Condition] ([ICD-10 Code]). At the time of service the record documents [objective finding: test or measure, score, date], which limited [specific function, for example walking a household distance or swallowing thin liquids]. Section [Section Number] of [Policy Name] covers this service when [criterion, quoted or closely paraphrased]. The [evaluation / progress note] dated [Date] documents [the matching finding].

[If the denial cited frequency or duration: The [visits / units] billed follow the plan of care dated [Date], which set [Frequency] for [Duration] toward [Measurable Goal]. Progress from [Baseline Measure] to [Current Measure] is documented in the note dated [Date].]

We ask that [Payer Name] overturn the denial and pay the claim. If the denial is upheld, please identify the specific criteria relied on, and we request a peer-to-peer review with a [Specialty] reviewer if the plan offers one.

Enclosed: denial letter dated [Date]; evaluation and plan of care; notes for [Dates of Service]; [letter of medical necessity dated [Date], if sent before treatment].

Sample 4: Missing authorization or retro-authorization request (CO-197)

Reason 197 (CO-197) is "Precertification/authorization/notification/pre-treatment absent." Three different facts produce it, and each needs a different paragraph: an authorization existed but was not matched to the claim, no authorization was required for this service, or none was obtained and you are asking for a retrospective review. Aetna routes "Outpatient service denials for no precertification" and "Retroactive authorizations" straight to appeal. Retro-authorization windows, where they exist, are narrow and set program by program; UnitedHealthcare's 2026 guide, for example, ties its retrospective windows to specific programs such as cardiac procedures and advanced imaging. ASHA publishes a "Lack of prior authorization obtained" appeal template for speech and audiology.

RE: [Reconsideration / appeal], authorization denial (CO-197), claim [Claim Number]
Patient: [Patient Name] · Member ID: [Member ID] · DOS: [Date of Service]
Service: CPT [CPT Code] · Authorization reference: [Authorization Number, if any]

[Payer Name] denied the claim above because no authorization was on file. [Choose the paragraph that matches the facts.]

[A. Authorization existed. Authorization [Authorization Number] was approved on [Approval Date] for CPT [CPT Code], [Number of Visits or Units] from [Start Date] to [End Date]. The date of service falls within that period and within the approved count. The approval is enclosed; please link it to this claim and reprocess.]

[B. Authorization was not required. On [Date], we verified benefits with [Payer Name] (reference [Call Reference Number] / portal response enclosed), and the service was not on the plan's authorization list for this member's product. Please reprocess the claim without the authorization requirement.]

[C. Retrospective review requested. Authorization was not obtained before the service because [the patient presented with [urgent clinical circumstance] / the patient's coverage with [Payer Name] was not known until [Date], when [reason]]. We contacted [Payer Name] on [Date], [Number] days after the service. The enclosed records show the service met the plan's criteria at the time it was provided, and we ask that [Payer Name] review it for medical necessity and pay the claim.]

Enclosed: [authorization approval / eligibility and benefits record / clinical notes for [Date of Service]]; remittance dated [Remittance Date].

Sample 5: Timely filing with proof of timely submission (CO-29)

Reason 29 (CO-29) is "The time limit for filing has expired." The only winning argument is proof, and UnitedHealthcare's 2026 guide spells out what proof must show: "The date the claim was submitted to us or another payer," "The date the claim was accepted by us or another payer," member identification, date of service and provider identification. It accepts an "EDI report," a billing software statement, or another carrier's EOB or denial, and warns that "claims that are rejected are not proof of timely filing." Original Medicare is different: CMS states a late-filing denial "does not constitute an 'initial determination'" and "is not subject to appeal," leaving only narrow exceptions such as Medicare administrative error. Use this timely filing appeal letter for commercial and managed care plans.

RE: Reconsideration, timely filing denial (CO-29), claim [Claim Number]
Patient: [Patient Name] · Member ID: [Member ID] · DOS: [Date of Service]
Original submission: [Original Submission Date] · Trace or claim number: [Clearinghouse Trace Number or Original Claim Number]

[Payer Name] denied the claim above as filed after the timely filing limit. The claim was first submitted on [Original Submission Date] and accepted on [Acceptance Date], within the [Number]-day limit in our agreement for a date of service of [Date of Service].

The enclosed [clearinghouse acceptance report / payer acknowledgment report] shows the submission date, the acceptance date, the member ID, the date of service and our billing NPI for this claim. [If another payer was billed first: The claim was first sent to [Other Payer Name], which denied it on [Denial Date] for [reason]. We submitted to [Payer Name] on [Resubmission Date], [Number] days after that denial; that EOB is enclosed.]

Because the claim was received and accepted within the filing limit, we ask that [Payer Name] remove the timely filing denial and process the claim.

Enclosed: [acceptance or acknowledgment report dated [Date]]; [other payer EOB or denial dated [Date], if applicable]; claim copy.

Sample 6: Coordination of benefits (CO-22)

Reason 22 (CO-22) reads "This care may be covered by another payer per coordination of benefits." UnitedHealthcare lists "Requesting review of member eligibility or coordination of benefits" as a reconsideration scenario, but the fastest fix is often a call: if the plan's record of other coverage is stale, have the patient update it with the plan, then send this letter with the proof. For Original Medicare, CMS says claims offices "can terminate records" when "MSP no longer applies (e.g., cessation of employment, exhaustion of benefits)," and those requests go to your Medicare claims payment office.

RE: Reconsideration, coordination of benefits denial (CO-22), claim [Claim Number]
Patient: [Patient Name] · Member ID: [Member ID] · DOS: [Date of Service]
Other coverage on file: [Other Plan Name], ID [Other Plan Member ID]

[Payer Name] denied the claim above as possibly covered by another payer. On [Date of Service], [Payer Name] was [Patient Name]'s [primary / secondary] coverage. [Choose one:]

[The other coverage on file, [Other Plan Name], ended on [Termination Date], before the date of service. The termination letter or eligibility response from [Other Plan Name] is enclosed.]

[[Payer Name] is primary under the plan's coordination of benefits rules because [reason stated in the plan's COB provision], as confirmed in the enclosed eligibility response dated [Date].]

[The primary payer, [Primary Payer Name], processed this claim on [Primary Payment Date]. Its EOB is enclosed so the secondary benefit can be calculated.]

[The patient updated their other-coverage information with [Payer Name] on [Date], reference [Call Reference Number].] We ask that [Payer Name] update its coordination of benefits record and reprocess the claim [as primary / as secondary using the enclosed primary EOB].

Enclosed: [termination letter / eligibility response / primary EOB]; remittance dated [Remittance Date].

Attachments That Carry the Argument

Aetna's appeal checklist is a good universal minimum: "A clear explanation of why you disagree with the decision," supporting documents, "The denial letter or EOB and original claim, for reference," and the denied codes or payments being disputed. Beyond that, match the evidence to the denial:

Denial	Attach	Leave out
CO-45 underpayment	Remittance, the fee schedule or rate page for the code, claim copy	Clinical notes; they do not prove a rate
CO-97 bundling	The note for that date showing separate times, sites or encounters; corrected claim reference	Notes from other dates
CO-50 medical necessity	Evaluation, plan of care, notes for each denied date, progress report, the policy section, any pre-service LMN	Psychotherapy notes
CO-197 authorization	Approval letter or number, eligibility and benefits record, notes showing urgency	Unrelated authorizations
CO-29 timely filing	Acceptance report showing submission and acceptance dates, other payer EOB	Rejection reports
CO-22 COB	Termination letter, eligibility response, primary EOB	Full insurance history

Send the records the dispute needs, not the whole chart. HIPAA's minimum necessary standard applies to disclosures for payment: a covered entity "must make reasonable efforts to limit protected health information to the minimum necessary to accomplish the intended purpose." Label each exhibit in the order the letter lists it.

Submitting the Request and Watching the Clock

1. Read the remittance line: group code, reason code, remark code and any policy number in the 835 policy segment. Confirm the claim was denied or reduced, not rejected.
2. Choose the remedy: a corrected claim for your own omissions, a Medicare reopening for clerical errors, and a reconsideration or appeal for a genuine disagreement.
3. Find the payer's name for the step and its deadline in that payer's guide; Original Medicare allows 120 days from receipt of the initial determination for a redetermination.
4. Fill in the general template or the matching sample, with one reason and one remedy per letter.
5. Assemble the exhibits in the order the letter lists them and remove anything the dispute does not need.
6. Submit through the payer's provider portal when it offers one; otherwise fax or mail to the address on the denial letter and keep the fax confirmation or tracking record.
7. Calendar a follow-up and the next-level deadline. A Medicare MAC generally decides a redetermination within 60 days of receipt.

Mistakes That Sink a Good Appeal

• Writing "please reconsider" with no reason code, no remedy and no exhibit list.
• Arguing medical necessity on a bundling denial, or bundling on a medical necessity denial.
• Appealing a rejected claim, or appealing a missing modifier that a corrected claim would fix.
• Sending a clearinghouse rejection report as timely filing proof.
• Resending the reconsideration packet unchanged at the appeal step.
• Missing the second clock: a reconsideration decision often starts a shorter appeal window.

Frequently Asked Questions

What should an insurance appeal letter include?

Include the patient name, member ID, claim number, dates of service, the disputed codes, the denial reason code, a one-sentence reason the decision is wrong, the remedy you want and a numbered list of enclosures. CMS requires a similar set of elements for a written Medicare redetermination, and Aetna lists nearly the same items for a reconsideration.

What is the difference between a reconsideration letter and an appeal letter?

A reconsideration letter asks the payer to take a second look at its own claim decision, usually for payment, coding or eligibility issues. An appeal letter asks for a formal review, often after a reconsideration is upheld, and should add new evidence rather than repeat the first packet. In Original Medicare the terms differ: the first level is a redetermination and reconsideration is the second level.

Can I use one sample appeal letter for reconsideration with every payer?

You can reuse the structure, but change the label, address and deadline for each payer. Use the payer's own name for the step in the RE line, send it to the address or portal on the denial, and attach any form the payer requires for mailed requests.

Should I send a corrected claim or an appeal letter for a missing modifier?

If the modifier was left off the original claim, a corrected claim is usually the right fix, and UnitedHealthcare states that a corrected claim is not a reconsideration. For Original Medicare, an incorrect modifier is a clerical error handled as a reopening. Use a letter when the modifier was on the claim and the line was still bundled.

Can a timely filing denial be appealed?

For commercial and managed care plans, yes, when you can prove the claim was submitted and accepted within the filing limit. Payers such as UnitedHealthcare accept an EDI acceptance report or another carrier's EOB but not a rejection report. For Original Medicare, CMS states a late-filing denial is not an initial determination and cannot be appealed.

Who should sign a provider appeal letter?

The rendering provider or an authorized representative of the practice, such as the billing manager, usually signs. For a medical necessity appeal, a signature or attached statement from the treating clinician carries more weight because the dispute is about clinical judgment.

Informational only, not legal, medical, or billing advice. Verify against current payer policy, your participation agreement and the member's plan before filing.

Draft It From Your Denial Code

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