MIB is a cooperative that serves 450 insurance companies, providing them information to help evaluate people applying for individually underwritten insurance policies (as opposed to group policies, which usually do not require individual review). Member insurers report information to MIB, and other member insurers can get access to that data, with your permission (you generally give it when signing your application).

MIB says its service can alert insurers to information — say, a condition like obesity, a bad driving record or even risky hobbies — that you may have “intentionally or inadvertently” neglected to report on an insurance application. An MIB spokesman, David Aronson, said the data-sharing helped keep insurance rates affordable by weeding out fraud.

If MIB has a file on you, the disclosure letter would describe what information it contained — say, an indication of high blood pressure or diabetes — and which insurer provided it, Mr. Aronson said. MIB says it does not retain actual medical records, like X-rays or lab reports; rather, it uses proprietary codes to describe medical conditions. The conditions may flag a possible problem if they do not match up with what was said on an application. Insurers cannot deny you coverage or raise your premiums based on such information alone, he said, but must do their own investigation to confirm it.

Here are some questions to consider when seeking annual disclosures:

Q. How can I determine which companies might have information about me — and whether I’ve found them all?

A. The federal Consumer Financial Protection Bureau maintains a list of these so-called specialty consumer reporting companies. More than 40 companies are on the list, although it’s not all-inclusive.

“There’s no definitive list, so it’s kind of amorphous,” said Chi Chi Wu, a lawyer with the National Consumer Law Center.

The list, which groups the companies into categories, is a good start — but it may not be worth your time to contact all of them. The bureau advises, however, that you may want to check with “some or all” of the companies if you have been a victim of identity theft. Other situations in which you might want to check with a company include those in which you are applying for insurance or a lease on an apartment, or in which you have applied for a new job and your potential employer asks for authorization to seek a background report.