IIUC, your (and the counterparty's) financial institutions will need to participate[0] in the FedNow program.
My bank (one of the big ones) does not participate. Which isn't too surprising as they issue lots of credit and debit cards, with which FedNow directly competes.
Hopefully, one of these days FedNow will be ubiquitous. While I'm not holding my breath, I'm also optimistic that it can and will work.
