Dear Liz: I am seeking your advice on how to maximize my credit score. Recently one of my cards was canceled for non-use, which reduced my available credit to $75,000. I use three other cards in rotation, never use more than 3% of my credit limits and always pay the balances off. I have made a few requests to have my credit limits increased in order to elevate my current 835 FICO score, only to be denied. I want to maintain as high a FICO score as possible (850). In order to do that I need to “play the game” … only I have no idea what the rules are! Could you please help me navigate this?

Answer: There is absolutely no practical benefit to having the highest possible credit score. You’ll get the best rates and terms once your scores are above the mid-700s on a 300-to-850 scale.

Regular readers can recite this next part by heart: Keep in mind that you don’t have one credit score. You have many, and they change all the time.

Even if you did hit 850 with one scoring formula from one credit bureau, you probably wouldn’t keep it for long or achieve the same number with all the other available scores.

You already know the most important credit rules: Use your cards regularly but lightly and pay your balances on time and in full every month. (Credit scoring formulas typically don’t “know” if you’re carrying a balance, so there’s no advantage in doing so.)

If you’re determined to hit 850, however, you could try using even less of your credit limit, applying for a new card to increase your available credit (the initial small ding to your scores would be short-lived) or simply waiting, since often the mere passage of time will add points to your scores.

Dear Liz: Have you ever covered the fact that the credit score that a person receives from the reporting agencies is entirely different from the one provided to lenders? The difference I discovered was 819 vs. 710. I’m a retired lawyer who represented investors in securities arbitration for 20 years, so not easily shocked or surprised by financial fraud, but I was.

Answer: The fact that there are many different scoring formulas has come up frequently in this column. What you consider to be fraud is actually a manifestation of capitalism.

Credit bureaus are private, competing companies. So are the creators of scoring formulas. Lenders and other companies that use credit scores have many to choose from.

FICO is the leading credit scoring formula, but rival VantageScore has gained market share in recent years.

Both types of scores come in multiple versions. The latest version of the FICO is the FICO 10, although the FICO 8 continues to be the most-used score.

Meanwhile, mortgage lenders tend to use much older versions of the FICO formula. Scores also can be tweaked for different types of lending, such as auto loans or credit cards.

Credit bureaus have created their own proprietary scores, as well. What this means is that the same underlying data — what’s in your credit report at a given credit bureau — can create significantly different FICO scores, depending on which FICO formula was used.

Even the same type of score, such as a FICO 8, could vary depending on which credit bureau’s information was used and when the score was “pulled” or created. The credit bureaus typically don’t share information with one another. Plus the information in your credit reports is constantly changing as information is added or deleted.

So it isn’t shocking that the score your lender used was different from the one the credit bureau provided you. What would have been surprising is if the number had been the same.

Dear Liz: I recently downloaded both my wife’s and my own credit reports. I noticed that, for a number of reasons, her report has much less information than mine. The probability is that I will die before her, so my question is whether you can suggest any ways to be sure she has a good credit rating after I’m gone. Do the credit reporting agencies give any weight to a spouse’s score?

Answer: They do not, unless the spouse is alive and a co-applicant.

The amount of information in a credit report doesn’t dictate someone’s scores, however. People can have good scores with only a few credit accounts, or bad scores with lots of accounts. Your wife should find out what some of her scores are to decide next steps. Her bank or credit card issuer may supply her with scores, or she could get free scores from one of the many sites that offer those. (FICO is the formula most often used by lenders, but VantageScore can give her a good idea how lenders view her, as well.)

If her scores are less than excellent (generally 740 and up), she could look for ways to improve them such as making all credit payments on time, using only a small fraction of her available credit and perhaps adding an account or two. Credit builder loans from credit unions can be a good way to build or rebuild credit.