An SR-22 is a certificate of financial responsibility required for some drivers by their state or court order in the United States). It is not an actual "type" of insurance, but a form filed with the state that serves as proof your auto insurance policy meets the minimum liability coverage required by state law. An SR-22 is not an insurance policy, but a filing, or an add-on, that is added to a personal automobile liability insurance policy). It is required for "high-risk" insurance policies, and not all insurance carriers offer SR-22 filings in all territories).
Not everyone needs an SR-22. Regulations vary from state to state, but usually, it is required by the court or mandated by the state only for certain driving-related violations, such as DUI convictions, reckless driving, accidents caused by uninsured drivers, and serious and/or repeat traffic offenses. If you need an SR-22, the courts or your state Motor Vehicle Department will notify you.
The SR-22 is filed by your insurance company with the state to prove that you have car insurance meeting the minimum coverages required by law. The SR-22 is typically required for three years in most states, and you will need to maintain continuous coverage during this period. If your policy lapses or expires during this period, your insurance company is required to notify the state, and you could lose your driving privileges.