Hi, Jacob,
"You must provide written verification that describes the domestic violence services provided to the client, and that describes the incidents of domestic violence the client experienced."
You will no doubt agree that, with both relative clauses sharing the same verb, it would be much better to say:
- You must provide written verification that describes the domestic violence services provided to the client and/as well as the incidents of domestic violence the client experienced/experienced by him/her.
With a different verb, the comma may be optional, but I would tend to omit it to preserve the restrictive nature of the clauses:
- You must provide written verification that describes the domestic violence services provided to the client and that specifies the incidents of domestic violence the client experienced.
In this case, however, I would use reduced relatives, which flow much better:
- You must provide written verification describing the domestic violence services provided to the client and specifying the incidents of domestic violence the client experienced.