CO-146 denial code: diagnosis invalid for the date of service

Claim adjustment reason code 146 says: diagnosis was invalid for the date(s) of service reported. The ICD-10-CM code on the claim wasn't a valid, billable code on the date the service was performed.

With group code CO, the patient can't be billed. Correcting the diagnosis and resubmitting usually resolves it.

• The code was deleted or changed in the annual update. ICD-10-CM codes change every year on October 1, and some mid-year updates take effect on April 1. A code that was valid in September may not be valid in October.
• The code was used before it became effective, for a date of service before its start date.
• The code isn't specific enough. ICD-10-CM requires the highest level of detail available; a category code that has more specific codes beneath it isn't billable on its own.
• A template or pick list still has old codes after an update.

1. Look up the code for the date of service in that year's ICD-10-CM code set.
2. Find the valid, most specific code the note supports.
3. Correct the claim and resubmit.
4. Update the template or pick list that supplied the old code.

• Check every diagnosis code against the date of service before sending.
• Update templates, favourites and pick lists before each October 1 and April 1 update.
• Code to the highest specificity the documentation supports.

CO-146 is a coding problem, so it is caught at billing.

Claira Health's AI agents catch this before the claim goes out, and tell your biller what's wrong in plain English. Your team sees only what needs a decision, and approves every step. On a 20-minute call, we’ll walk through it using one of your own denials.

Related: CO-11, diagnosis inconsistent with the procedure. Book a 20-minute call before your next October update.