The feature is available now in 22 US cities for businesses using Square, and customers have to be preapproved before they can start financing. Most customers will be able to see if they’re approved instantly, but there will be cases in which approval can take one to two business days. Once approved, customers will receive a one-time use digital card number they can show to merchants to pay for their purchases. There are no service fees involved, and customers will be able to see the total cost of their payment plans up front for each monthly payment available.

https://www.theverge.com/2018/10/4/17937906/square-installments-monthly-payment-seller-customer