This paper studies how small firms respond to monetary policy and recession shocks. A large literature modeling firms with financing constraints examines how firms adjust their borrowing. However, recent empirical work has shown that what is unique to small firms is their prevalent use of credit cards. Using new micro data on small firm credit card use, I study credit cards' dual role as both a financing tool and a liquidity service. With this data, I document a set of facts on small firm financing in the U.S. from 2014 to 2021. First, I show that credit card balances, limits, and slack (unused card capacity) increase with firm size, with balances increasing less than limits and slack. I also show that slack co-moves with aggregate deposits in the years from 2014 to 2019 before diverging during the start of COVID. To interpret these facts, I develop a quantitative model of constrained firms with liquidity. The model shows that firms with less wealth use credit cards more for borrowing and have less card slack and deposits for liquidity, while wealthier firms focus more on liquidity management. Finally, I show that monetary policy affects small firms by raising the cost of liquidity. This mechanism amplifies output responses among larger firms relative to smaller ones.