Banks can borrow reserves from other banks or the lender or last resort. They usually do keep some reserves around for liquidity, but as little as possible beca

Banks can borrow reserves from other banks or the lender or last resort. They usually do keep some reserves around for liquidity, but as little as possible because reserves don't make as much return just sitting in an exchange settlement account as they do if they lend them to other banks or buy Government bonds with them. Fractional reserve in general isn't really a thing in modern banking. The US still does have a reserve requirement but pretty much the rest of the world relies on capital adequacy ratios (some capital is usually stored as reserves in exchange settlement accounts but it doesn't have to be).