Your FBO account at the sponsor bank earns interest, paid monthly. On a ₦100,000 average daily balance at 6% APR, that's about ₦500/month of interest. THAT'S REAL MONEY. Most neobanks treat float income as the largest single line item after interchange. The accounting question: when the sponsor credits your FBO with float interest, where does it go? Three policies exist, for simplicity, this lesson takes the most common: you keep it all as platform revenue. Booking it correctly preserves your sum(user wallets) = FBO invariant after sweeping.