Car insurance is designed to provided compensation for someone in the event that she must pay auto-related expenses. Insurance companies issue policies in advance. This is because the insurance company will be forced to pay out money in the event that an accident occurs. When a policy is issued in advance, both the insurance company and the person buying the policy do not know whether an accident will occur and damages will be assessed.
When an accident occurs, insurance companies must pay out money to cover the accident or other loss. When a person buys insurance, he is securing himself against future financial losses. The cost of the insurance is usually considerably less than he would receive in the event of an accident. While, legally, a person might be able to buy retroactive insurance, no insurance companies sell it, as it would not make financial sense for the company.
Companies do not sell retroactive insurance because anyone purchasing a policy for a past period of time is highly likely to file a claim. This is one of the few reasons that a person would have to buy retroactive insurance. If the person did not wish to use the policy to cover a past accident, why would he buy the policy?
In some cases, a person may attempt to buy car insurance to retroactively satisfy a legal requirement to hold insurance. Even if a person does manage to convince a company to write him a retroactive insurance policy, this will not satisfy the legal requirement for holding insurance at the time. If he was cited for driving while uninsured, he will not be allowed to escape the penalty by buying insurance at a later date.