I suggest that what is stated in the service agreement between this firm and the TPA is critical. Hopefully this is not a situation where a service agreement isn't even used. (That thought makes me cringe.) In our agreement we say exactly what we do and what it costs. We also stated that prior errors, issues not specifically related to our service, and/or issues arising from acting in a manner that ignored or was contrary to written advisement we provided, is not our liability. Given the big fat target placed upon the back of the TPA, I just think that as much as possible the terms of service must be clearly defined. Then, the claim that the TPA is somehow responsible for the payroll processing, when that is clearly an issue not under the TPA's purview, is totally baseless. So check out the agreement in effect, and modify future agreements as needed given this new experience. My 2 cents.