Consumers have been getting letters from their credit card issuers announcing deep cuts in their credit lines.

But not to worry, says a new study by FICO (formerly Fair Isaac), the creator of the widely used credit-scoring system. If you don't carry a high balance and you are a good credit user (paying off your balance every month), the cuts might hurt your feelings but will have minimal impact on your FICO scores.

"Our study suggests that lenders are using a scalpel and not a hatchet to trim their revolving credit exposure," said Mark Greene, chief executive of FICO.

FICO found that about one in five consumers had their credit lines reduced. In all, between October 2008 and April of this year, the available revolving credit was sliced for an estimated 33 million US cardholders. That was up from an estimated 25 million cardholders between April 2008 and October 2008. The average reduction in credit limit was $5,100.

In the latest sampling of the 33 million who had their credit limits reduced, researchers found that the credit reports for nearly nine million contained recent negative credit dings such as late payments. It was such information that may have prompted lenders to reduce those customers' limits.

Ah, but you may be inclined to say those folks got what they deserved. So what about the good users with no reported negative information in their credit files?

FICO found that 24 million cardholders whose limits were cut did not have any new negative information in their files. In fact, this group had a median FICO credit score of 760, on the scoring model's 300-850 score range. For the 24 million, this is what happened to their scores after their limits were reduced:

• 12 million had an increase in their scores after their credit line had been lowered.

• Of 8.5 million, most saw their typical scores drop 20 points or less.

• 3.5 million had no appreciable change in their FICO scores.

Of course, it would only be fair to point out that FICO has a vested interest in the survey outcome. After all, most of the lenders that are doing all the slashing of credit limits are relying on the credit scoring models to determine who is creditworthy, which in turn is part of the reason the issuers are cutting credit lines. Still, the study may help ease the fears of the many people who now are concerned about not having access to thousands of dollars in debt — even if they don't plan on using it.

Many consumers have told me they're so outraged that their issuers have lowered their limits that they want to fight back by closing their accounts. But what would this do to their scores? I put that question and a few others to Craig Watts, FICO public affairs director. Here's what he had to say:

Q: Will it lower my score if my lender (and not me) closes my credit account?

A: No. It doesn't matter to your FICO score who closed the account.

Q: Will closing a card account shorten my credit history?

A: No. Credit bureaus keep records of closed accounts in consumer credit files for years (seven years for negative information, longer for positive information). So a closed account will continue to appear on your credit report where it is accessible for the calculation of FICO scores. Those scores do consider the age of both open and closed accounts when determining the length of your credit history.

Q: Will closing a card account increase my credit utilisation rate, thereby causing my score to drop?

A: Not necessarily. A large percentage of adults (roughly one-third, based on FICO's studies) habitually uses less than 10 percent of their total revolving credit. Having a utilisation ratio that low means, among other things, that closing a card account is less likely to change your overall utilisation rate. The situation changes if you had only one card account to start with, or if you have multiple cards with high reported balances, and so on.

Q: If I close a card account that still shows a balance, how will that affect my score?

A: The reported outstanding balance of your closed account will continue to influence your overall credit utilisation rate, so paying off that balance should continue to be a priority. If you miss a payment and are reported 30 days late on that closed account, the delinquency will hurt your score. So to maintain a good score, you should treat that balance on the closed account with the same respect that you give your active credit accounts.

Whether a card closure or credit line cut will affect your FICO score depends on what else is in your credit report. But at least the FICO study shows that if you're using credit as wisely as possible, reduced credit limits shouldn't give you a credit panic attack.

Readers can write to Michelle Singletary c/o The Washington Post, 1150 15th St., NW, Washington, D.C. 20071. Her e-mail address is singletarym@washpost.com. Comments and questions are welcome, but due to the volume of mail, personal responses may not be possible. Please also note comments or questions may be used in a future column, with the writer's name, unless a specific request to do otherwise is indicated.