(NBC News) – Suffice it to say your FICO credit score is one of the most important numbers in your financial life.

“This is used in about 90% of lending decisions,” said Ted Rossman with creditcards.com. “It’s going to determine whether or not you get that loan or line of credit in the first place. And, if you do, the interest rate you’ll pay.”

But now, the way your FICO score is determined has changed to what experts call trended data.

If it’s just one month out of 12 where your spending is well above normal, then it’s not going to hurt your credit rating. But fall behind paying your bills 3 or 4 months in row, get ready to pay more.

“Your debts creeping up, you’re starting to fall behind your bills; trended Data is going to penalize somebody like that,” said Rossman.

Experts say the best way to avoid a hit from the changes is to simply pay your bills on-time.

Read more here.