We are two families (A & B) going for a nanny share (1 child each). A will be the principal employer where her paystubs come from (children will always stay at A's house, A has the insurance and EIN). Now both A & B would like to claim FSA, for A its easy. But is it also possible for B, and if so how? In a quick internet search I found confusing information about what to provide from whom. Does B list A or the nanny?