German Law/Child Support after 18
My husband's daughter recently turned 18, and has been living in the US for the last few years with her German mother and her new American husband. She should start her senior year here, however we are not sure if she moved back to Germany. There is a German order stating we pay her mother the child support. However, both the mother and child states we can directly put it into the child's account. Do we have to have something from the courts in writing for this? I just do not want to pay and then be told we did it incorrectly and have to repay.
your husband has nothing to worry about.
If he has an e-mail or a letter from mother and/or child (she is an adult now and thus no longer legally represented by her mother) about the changed account, that is absolutely sufficient. Nobody could come after him for back-pay (as long as he keeps receipts or his bank statements as evidence, of course).
I should also mention that under German law (which only applies if the daughter has moved to Germany), both parents are financially liable. Depending on the income of the mother, this could reduce the financial obligation of your husband towards his daughter. Also, once the daughter starts a professional training and receives a salary or once she receives government support for attending university (in Germany, students don't pay tuition fees but actually receive a government stipend while studying), that income will be deducted from her child support claim.
Because there is a court order, it may well be that the actual claims are lower than the claims according to the court order. In this case, it would be preferable if the parties would come to an agreement amending the court order, for otherwise your husband would need to file a petition to have it amended. But that also depends on the exact wording of the court order, which I would need to take a look at before giving more detailed advice.
All the best!