Denial code CO-182: modifier not valid on that date

Also printed as PR-182, OA-182, PI-182 or 182

CO-182 means: The modifier wasn't valid on that date. Usually the provider's billing office fixes this by correcting and resubmitting the claim. Call them first. An in-network provider usually shouldn't bill you while it is sorted out. Can they bill you for it? Usually no. CO means the provider has to write this off under its contract with the plan. If the provider can't fix it, I can draft an appeal letter.

Checked 27 September 2026 against the X12 code listsProvider's billing office

Who usually fixes it

The provider's billing office.

What CO-182 means

The modifier wasn't valid on that date.

How CO, PR, OA and PI change it

The letters in front of the number are the group code. They say who the plan thinks owes the amount, so they change whether the provider can bill you, not what the code means.

Code	Can the provider bill you?
CO-182 Contractual obligation	Usually no. CO means the provider has to write this off under its contract with the plan.
PR-182 Patient responsibility	Yes. PR means the plan says this amount is yours, unless the decision changes.
OA-182 Other adjustment	It depends. Ask the provider's billing office.
PI-182 Payer-initiated reduction	Usually no. PI means the plan reduced it under its own policy.

What to do next

Usually the provider's billing office fixes this by correcting and resubmitting the claim. Call them first. An in-network provider usually shouldn't bill you while it is sorted out.
Call the provider's billing office first. A corrected claim often fixes a coding error faster than an appeal, but still file the appeal before the deadline.
Your doctor can often file the appeal or request a peer-to-peer review with the plan's doctor. It is worth asking.

What to send with an appeal

A copy of the denial notice or Explanation of Benefits.
A letter from your doctor explaining why the care is needed (a letter of medical necessity).
Relevant medical records, test results and notes on treatments already tried.
The itemized bill and the corrected claim or a note from the provider's billing office.
Notes of phone calls: date, time, who you spoke to and what they said.
Keep copies of everything, send it in a way you can track, and ask the plan to confirm it arrived.

Draft the appeal letter

Appeal My Claim drafts a “coding or billing error” appeal letter that quotes CO-182, with [brackets] for anything you have not filled in. You review it and send it yourself. Write the letter.

Appeal steps and deadlines

You have 180 days from getting the denial notice to file an internal appeal. The plan decides within 30 days for care you haven't had, 60 days for care you've had, or 72 hours if urgent. After a final denial, you have 4 months to ask for an external review.

Read the denial notice. It must say why the claim was denied and how to appeal.
File an internal appeal with your plan within 180 days of getting the notice. Ask your doctor for a letter explaining why the care is needed.
If the internal appeal is denied, ask for an external review by an independent reviewer within 4 months of that final denial. Your plan must accept the reviewer's decision.
If your situation is urgent, ask for an expedited appeal. You can ask for an urgent external review at the same time as the internal appeal.

Step	File within	Decision due
Internal appeal	180 days from when you got the denial notice	30 days for care you have not had yet, 60 days for care you already had, 72 hours if urgent
External review	4 months from the final internal denial	45 days standard, 72 hours or sooner if urgent

Dates are a guide. Count from the date on your notice, or the day you received it where the rule says so, and use any date printed on your notice if it differs. File early and keep proof of when you sent it.

Medicare, Medicare Advantage, Part D and Medicaid have their own steps and deadlines:

Quick answers

What does denial code CO-182 mean?: The modifier wasn't valid on that date. Usually the provider's billing office fixes this by correcting and resubmitting the claim. Call them first. An in-network provider usually shouldn't bill you while it is sorted out.
Can the provider bill me for CO-182?: Usually no. CO means the provider has to write this off under its contract with the plan.
What is the difference between CO-182 and PR-182?: The reason is the same: The modifier wasn't valid on that date. The group code changes who pays. CO-182: Usually no. CO means the provider has to write this off under its contract with the plan. PR-182: Yes. PR means the plan says this amount is yours, unless the decision changes.
Who fixes CO-182?: The provider's billing office. Usually the provider's billing office fixes this by correcting and resubmitting the claim. Call them first. An in-network provider usually shouldn't bill you while it is sorted out.
How long do I have to appeal CO-182?: For most private plans: You have 180 days from getting the denial notice to file an internal appeal. The plan decides within 30 days for care you haven't had, 60 days for care you've had, or 72 hours if urgent. After a final denial, you have 4 months to ask for an external review. Medicare, Medicaid and other plans have their own deadlines, and the date on your own notice is the one to follow.

Codes are from the national X12 lists, in plain words. Your notice and your plan are the final word on why a claim was denied. General information, not legal advice.

Sources

Ask Appeal My Claim yourself

Type any code from your Explanation of Benefits, like CO-50, PR 204 or N130, and get it in plain words, with a letter when an appeal fits. Open Appeal My Claim, free, no sign-up.

In Claude or any app that takes MCP connectors, add https://goodturn-mcp.pages.dev/appealmyclaim/mcp and ask: “My EOB says CO-182, what does that mean?”