For Christmas shoppers that signed up for those buy now, pay later plans, the holidays are over and it’s time to pay up—maybe more than you expected. So, Consumer Reports is here to make sense of these short-term loans with important advice on how to dodge costly fees and what to do next time.

Digital payments company Square Inc. says it has agreed to acquire Afterpay, which provides a “buy now, pay later’’ option for merchants, in an all-stock deal valued at about $29 billion.