Monthly Coverage

• Car insurance policies offer a person coverage for accidents over a set period of time. When a driver is buying personal insurance for his own vehicle, he generally purchases a long-term policy, as he will likely be keeping the car for an extended period of time and does not want to shop for a new policy each month. Yet, if the driver wants coverage for only a single month, some companies will offer this to him.
  
  

Company Policies

• Whether a person can buy 30 days of coverage for a vehicle depends on the policies of the insurer. While some insurers are willing to extend coverage for short period of time, the nation's largest provider of auto insurance, Progressive, generally does not. However, all major rental car companies sell insurance by the day. This means that a person would likely be able to buy 30 individual days of insurance coverage for the rental vehicle.
  
  

Rates

• Generally, the shorter the auto insurance policy, the higher the premium the driver is forced to pay on the policy. This is true for several reasons. First, insurers have an incentive to sell longer policies. As with many items sold in bulk, insurers ofter a discount for a longer policy. Secondly, insurers may believe that a person taking out a short-term policy may be more likely to engage in risky activity and therefore presents more risk of drawing a claim against the policy. To offset this risk, the insurer must hike up the price of the policy.
  
  

Payment

• Even if a car insurance policy is not available for only 30 days, most insurers allow people to make monthly payments on a six-month or year policy. So, while the person may be purchasing coverage for a full six months, he is paying for only a month at a time. However, companies usually charge a premium for this method of payment. Also, people are usually obligated to pay for the full term -- they cannot pay for several months and then opt out.