Does temporary car insurance exist?

Why don't US insurers sell one-week car insurance?

Personal auto rates are filed with each state's insurance department in six- and twelve-month terms, and a carrier cannot charge a rate it has not filed. Very short policies also attract drivers who already expect to need coverage, so the risk pool prices the product out of existence before regulators ever see it.

Search results promising one-day cover almost always lead to a quote form for a standard six-month policy, for a non-owner policy, or for a rental product. The exception is commercial: some insurers write short-term policies for delivery and rideshare work, and those are business auto products with their own eligibility rules, not consumer car insurance.

Source: Texas Department of Insurance, auto insurance guide

What can you buy instead for a few days or weeks?

Four things fill the gap: a non-owner liability policy for drivers without a car, the rental company's supplemental liability at the counter, permissive use of the owner's policy when you borrow a car, or being added to a household policy as a listed driver for the weeks you need it.

Can you cancel a six-month policy early instead?

Yes. A personal auto policy can be cancelled at any time, and most states require the insurer to refund the unearned premium, usually pro rata. The catch is the gap it creates: a lapse in continuous coverage raises the rate you are quoted next time and, where an SR-22 is already on file, can restart the filing period.

Registration rules run in parallel with insurance rules. In most states a registered vehicle has to stay insured whether or not anyone drives it, and the insurer reports the cancellation to the state, so cancelling to save two months of premium can cost a registration suspension and a reinstatement fee.