How to appeal a denied insurance claim: step-by-step for medical practices
To appeal a denied claim: confirm the denial reason on the remittance, check that an appeal (not a corrected claim) is the right fix, gather the evidence that answers the payer's stated reason, send a signed appeal letter with that evidence through the payer's stated channel before the filing deadline, and track the payer's response clock until you have a decision in writing.
What should you do first when a claim is denied?
Read the remittance advice before anything else. The claim adjustment reason code (CARC) tells you why the payer denied the claim, and that reason decides everything that follows: whether to appeal, what evidence you need, and which deadline applies.
Look the code up in the denial-code reference — each code page gives the verbatim meaning and whether the denial is worth appealing.
Is an appeal or a corrected claim the right fix?
If the claim itself was wrong — a data-entry error, a missing modifier, the wrong date of service — submit a corrected claim instead of an appeal. Appeal when the claim was right and the payer's decision was wrong.
What goes into the appeal?
A signed letter that identifies the claim, states what you are asking the payer to do, answers the payer's stated denial reason directly, and attaches the proof: the remittance showing the denial, the records that support the service as billed, and documentation for every fact the letter asserts.
Where do you send the appeal, and by when?
The payer's provider manual states the appeal address or portal and the filing deadline — and the deadline depends on who regulates the product, so the same payer can hold different windows on different plan types. File well before the deadline and keep proof of submission.
What happens after you file?
Payers owe a decision within a stated response window. Calendar that clock when you file; if the decision does not arrive, follow up in writing, and if the appeal is denied again, move to the next level of review rather than refiling the same letter.