Since the financial crisis, major central banks have introduced negative interest rates with the help of tiered reserve remuneration. We theoretically and empirically investigate monetary policy implementation via reserve tiering using a unique bank-level dataset from Switzerland. We find that reserve tiering can successfully be used to steer short-term interest rates. Furthermore, reserve tiering helps maintain sufficient activity in the interbank market, which is key for financial stability and reliable interest rate benchmarks. Due to frictions such as collateral constraints, trading costs, and window dressing around regulatory reporting dates, not only the aggregate level of reserves but also the reserve distribution matters for monetary policy implementation.