Credit scores for decades have been based mostly on borrowers’ payment histories. That is about to change. Fair Isaac Corp. (FICO 0.13%), creator of the widely used FICO credit score, plans to roll out a new scoring system in early 2019 that factors in how consumers manage the cash in their checking, savings and money-market accounts. It is among the biggest shifts for credit reporting and the FICO scoring system, the bedrock of most consumer-lending decisions in the U.S. since the 1990s.