Here’s a reference to the denial reasons for the claim receiving the CO16 code. I’m not certain that this is an authoritative reference but it should get you started figuring out which claim you need to exclude from the batch file you submit.
I could be wrong but I believe that when importing payments from an ERA you don’t have control over which ones are applied, they all are.
If that is the case your remedy is to exclude the bad claims from the claim batch file that you submit.
As far as choosing to not post certain claims the following wiki pages tell how that would be done.
First, this step is how to assemble the claims to be posted.
When they are all listed on the screen, locate the one with the error in it and simply DO NOT select it. When you generate the list of claims to post, they can be either individually selected (rectangle below) or all selected (oval). If you ‘Select All’, you can exclude the offending claim by de-selecting its checkbox.
Also see end of section ‘Claims Creation’ starting here: