To verify that a payer offers eligibility checks, you can check TriZetto's (or other clearinghouse's) payer list.
If there is a blue circle with a white check listed, the payer offers RTE checks. The yes/no in the "enrollment required" column will let you know if paperwork is required before the client can use RTE.
ePS (eProvider Solutions) - https://www.eprovidersolutions.com/index.php/payer-list
TriZetto - https://payers.gatewayedi.com/payerlist/default.aspx
Change Healthcare (fka Emdeon) - https://payerfinder.changehealthcare.com/npd?adobe_mc=MCORGID%3D26CD3A665C7D19990A495D73%2540AdobeOrg%7CTS%3D1675691787
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To check to see what services a payer offers - google "Trizetto payer list" (or any other clearinghouse https://payers.gatewayedi.com/payerlist/default.aspx). Using the image above, look up the payer by either name or payer id in the box on the left, in the blue shading labeled Payer, and click Create Report.
If the payer offers the service, it will be listed under the "available transaction" column. Each colored oval represents a different service. For example, the green C stands for Claims. The column to the right labeled "enrollment required" will tell you if the payer requires enrollment for that particular service. Many payers do not require enrollment to submit claims but do require enrollment to receive ERAs (orange circle with a dollar sign). If you hover over the colored circle, it will tell you what category it is.