It’s easier than ever to check your credit score. Your banks, credit union, credit card issuer, and a handful of online memberships sites all offer free access. However, while it generally doesn’t make sense to pay for something you can get for free, there are times when you might want to open your wallet — such as when you’re applying for a mortgage.

THERE ARE MANY CREDIT SCORES AVAILABLE

To start, it’s important to realize that there are many different credit scores. A credit score is like a grading program that looks over one of your credit reports to determine your grade, and these programs get updated over time. Currently, FICO makes dozens of scores for lenders to use when reviewing applications, and VantageScore, a major rival in the U.S., offers four different credit scores.

FICO and VantageScore credit scores both use similar scoring criteria, create a score based on the information in one of your credit reports, and (for the most part) use a 300 to 850 score range. As a result, the scores tend to track in the same direction. For example, if your FICO Score 8 (one scoring model) is improving over time, your FICO Score 9 and VantageScore 4 could be as well.

The tricky part is you don’t know which scoring model the creditor will use, and which of your three credit reports (from Experian, Equifax, or TransUnion) your score will be based on. So, even if you check one of your credit scores before applying for a loan or card, the creditor might use a different score when reviewing your application.

WHEN TO BUY A CREDIT SCORE (AND WHICH SCORES TO BUY)

An exception is when you apply for a mortgage. Most mortgage lenders follow Fannie Mae and Freddie Mac underwriting guidelines, which require the lender to use specific credit scoring models.

Mortgage lenders try to review three credit scores, one based on each of your credit reports, and use the middle score to determine your eligibility for a mortgage. The scores they use are:

• FICO Score 2, also known as Experian/Fair Isaac Risk Model V2SM
• FICO Score 5, also known as Equifax Beacon 5.0
• FICO Score 4, also known as TransUnion FICO Risk Score, Classic 04

Because you know which scores most mortgage lenders will use, you might want to check your scores if you want to buy a home. However, these scores aren’t available for free.

You can buy them directly from FICO by visiting the MyFICO website, or you may be able to find third-party companies that include the scores. Additionally, your mortgage broker or lender may be able to check your scores, although the check might count as a hard inquiry (the type that may hurt your scores).

HOW TO GET YOUR CREDIT SCORES FOR FREE

You can check and monitor several of your credit scores for free. Although these won’t be the exact scores mortgage lenders use, other types of creditors may use these scores, and they can give you a general idea of where you stand in terms of credit scoring.

Some of these programs also include free credit monitoring, which can notify you if there’s a new account or suspicious activity on your credit report. This could be an indication that you’ve been a victim of identity theft, helping you act quickly to close the account and limit the impact.

Here’s an overview of some of the major free sources, which credit scoring model they offer, and which credit reports the scores are based on. We’ve also limited the list to services that also include free credit monitoring, which can send you an alert if there’s a significant or suspicious change to your credit report.

You can also get free credit scores from hundreds of banks, credit unions, credit card issuers, and other financial institutions through VantageScore and FICO programs. However, the scores might not come with access to your credit reports or credit monitoring.

THE FREE SCORES ARE USUALLY ENOUGH

You might want to buy access to specific credit scores while shopping for a home. But generally, the free credit scores you can get are enough to help you determine where you fall in the scoring range. Regardless, you can improve most scores by paying down credit card balances and make your monthly payments on time.