What’s changing?

Some of the changes, like carrying a personal loan as well as credit-card debt, affects both new scores. But there are more substantial changes involving the FICO 10 T version.

For example, instead of looking at just a static month of your balances, FICO 10 T will look at the past two years or more, which will give lenders more insight into how you’re managing your credit over time. That should mean your scores will better reflect the trajectory of your behavior. (VantageScore, a lesser-known score provider that is a joint venture of the three big credit-reporting companies, has already incorporated this into its formula.)

There are other changes, too. FICO 10 T will weigh recent missed payments more heavily and penalize those who use a high percentage of their overall available credit for long periods.

That could have consequences for a person who leans on credit cards during times of distress, like a job loss. “But that person is probably a bad credit risk, unfortunately,” said Chi Chi Wu, a staff attorney at the National Consumer Law Center.

She said she worried that lower scores for such consumers could add to their troubles, making car insurance more costly or hurting their chances of finding housing — and make it harder for them to get back on their feet.

How and when will the changes affect me?

Most consumers, or 110 million people, will see modest swings, if they see any change at all, according to FICO. But about 40 million people who already have favorable scores are expected to gain about 20 points, while another 40 million with lower scores will probably see a drop.

But not every lender will use the new scores right away.

People applying for most mortgages will not be affected, at least for now. That’s because home loans guaranteed or backed by Fannie Mae and Freddie Mac, which include the vast majority of mortgages, are still required to use older versions of the FICO score.