Are banks required to obtain beneficial ownership if a wire is conducted on their existing business customer? Or is this something that is risk-based and the bank decides if it wants to request it.

A wire transfer is not the establishment of a new account. As part of the bank's ongoing monitoring procedures for CDD/EDD, if the bank identifies a change in activity for a legal entity that leads it to conclude that a change in ownership may have occurred, as part of the ongoing monitoring requirement it should request an updated certification.

The decision of what constitutes a change in behavior will be inherently subjective based on the normal and expected activity for each customer.

Agreed with above - no account

My response is based on comments I have seen from some training presenters that a large wire to or from an account that has never had large wires before would constitute a change in the risk profile requiring the bank to obtain updated beneficial ownership info on the existing customer. I do not subscribe to this line of thinking but it may have been the genesis of the OP’s question.

Also a non subscriber.

The only triggering event for obtaining the certification under the regulation is the opening of a new account. Based on guidance issued several years ago, banks should already know the beneficial owners of their "higher risk" customers. I can make a case that, for the sake of form over substance, banks should periodically update the beneficial ownership information for those higher risk customers; e.g. during annual reviews, if they have not opened an account in the interim.

Beyond that, obtaining "new" unconfirmed information because of XX is a ridiculous waste of time. Using a wire transfer as a triggering event would be a good example. (It would also defy an intelligent explanation for the request you could offer to the customer; e.g. you sent/received a wire transfer so we need to know who owns your company?)