How do insurance companies know if you have a pre-existing condition?

How do insurance companies know if you have a pre-existing condition?

Policies Differ from Insurer To Insurer: There are some insurance providers who, while determining an applicant’s pre-existing medical condition, will consider their medical history in entirety. Some other providers may only consider at the applicant’s medical history for a period dating back to the past 4 years.

See also  How do I change my VSP email?