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.

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