Hi Zhengyuz417,
This question has come up before and basically the answer is the same. Assuming this is a manual entry and Square is your CC Processor, you'll need the CVV. This is a requirement via Square.
If you're setup to retain customer's CC details from previous transaction (Card On File), that may be your work around. There's also an option for Bank Account on File. You would just need the customer's name.
Note, if you are the customer and making an online purchase via another business, the business may not require the CVV as they have other means to verify your Card. However, Square does require the CVV.
jk
