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Denial Decoder

Last reviewed October 17, 2026

Written by Aptiva Health Editorial TeamReviewed by Taylor Sorrels, Esq. and Crystal Brake, RCM DirectorEditorial & review standardsHow we research

In short

The Denial Decoder turns the wording on a denial letter or EOB into plain language. Pick one of six common reasons, or paste the words or a reason code. You see what the reason usually means, the likely appeal route, a matching guide and, if you add your state and plan type, a filing deadline.

Denial Decoder

Pick the reason on your denial letter, or paste the wording or a claim code from your letter or Explanation of Benefits. See what it usually means and the likely way to appeal.

Everything you type stays in your browser. Nothing is sent or saved.

What does your letter say?

For example: “not medically necessary” or “CO-197”. Don’t include your name or member ID.

See your deadline (optional)

Denial letters often use hard insurance words. The Denial Decoder turns them into plain language and points you to the right guide.

How to use the Denial Decoder

  1. Find your letter. Have your denial letter or Explanation of Benefits (EOB) in front of you. Look for the line that gives the reason.
  2. Pick or paste the reason. Choose one of six common reasons (listed below). Or paste the wording, or a claim adjustment reason code, from your letter or EOB.
  3. Add your state and plan type. This step is optional. Pick Kentucky, Indiana or another state, and your plan type, to see a filing deadline.
  4. Read the result. See what the reason usually means and the likely appeal route.
  5. Open the matching guide. Each result links to a guide that explains what to send.

The six reasons are: not medically necessary, no prior authorization, out of network, experimental or investigational, coding or billing error, and benefit limit reached.

What your results mean

What the reason usually means. For example, “not medically necessary” usually means the plan decided the care did not meet its own rules for that service. Your letter may mean something a little different, so compare the result with your letter.

The likely appeal route. Most denials start with an internal appeal to your plan. Some can then go to an independent reviewer. Federal rules allow outside review for denials based on medical judgment. That includes medical necessity and experimental or investigational decisions (45 CFR 147.136(d)). In Kentucky, outside review mainly covers medical necessity and experimental or investigational denials (KRS 304.17A-600). A denial based on a plan limit or exclusion may go first to a Department of Insurance review (KY DOI: Appealing a Denial). In Indiana, payment and contract grievances stay internal; they are not eligible for outside review (IC 27-8-29-12).

The matching guide. For example, a medical necessity result links to Denied as “not medically necessary”. A prior authorization result links to Denied for missing prior authorization.

Your filing deadline. If you picked a state and plan type, the tool shows the deadline from the Hub’s deadline table. For example, in Kentucky most plans must allow at least 180 days to file an internal appeal (KY DOI UM Review Guide (2026)).

Where the deadlines and rules come from

The tool uses only official sources:

For out-of-network denials, the tool also notes federal protections. Plans must cover emergency care without prior authorization, even out of network (45 CFR 149.110(b)(1)). The No Surprises Act also protects you from some surprise out-of-network bills (CMS: Medical bill rights).

What this tool can’t do

  • It can’t read your plan documents or know your plan’s own rules.
  • It can’t tell you whether your appeal will win.
  • Pasted wording is matched to common phrases. Unusual wording may not match, or may match wrongly. Pick the reason that fits best, or call your plan.

Your denial letter must give the specific reason and the plan rules it relied on (29 CFR 2560.503-1(g)(1)). If the reason is unclear, you can ask your plan to explain it.

Your privacy

Everything you type or paste stays in your browser. Matching happens on your device. Nothing is sent to Aptiva or saved. If you choose the optional “email me” feature, only your email address, state, plan type and the tool name are sent. Please don’t paste names, member ID numbers or other personal details.

Frequently asked questions

What is a claim adjustment reason code?

It is a short code on many EOBs that says why a claim was not paid in full. You can paste it into the tool to see what it usually means.

Can I trust the deadline the tool shows?

It comes from official sources, but your plan may allow more time. Always check the deadline on your denial letter.

Can I get the codes and records the plan used?

Yes. When you ask, plans must give you free copies of the records used for your claim. They must also give you the diagnosis and treatment codes and what they mean (45 CFR 147.136(b)(2)(ii)).

What should I use next?

The Appeal Route Wizard shows your full appeal route. The Appeal Deadline Calculator turns your letter date into real dates. The Appeal Letter Builder helps you draft a letter. For the full process, see the Coverage & Appeals Center.

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