The identifier for one of your providers is going out without an NPI. If you do not have an NPI entered, Therabill will use the Tax ID that you have on file for the provider as the identifier. While some payers will allow this (which is why Therabill will enter it), most payers require the NPI of the provider to be entered as the identifier.
How to Fix in Therabill
The providers NPI is entered on the add / edit provider form. You can access this form by putting your mouse over Providers in the top green navigation bar and then choosing Provider List in the sub-navigation menu. Once on your provider list, click the blue pencil icon associated with the rendering provider. The edit provider form will open up. Enter the NPI on the edit provider form and then click one of the save buttons at the bottom of the form.
From the error page
If you are currently on the claim error page, you can quickly open up the edit provider form by clicking the edit icon next to the rendering provider listed under the Claim Information section.
You can resubmit the claim from the error page by clicking the Resubmit Electronically button at the top of the claim error page.