An SR-22 is a form that is usually required to be shown as insurance proof when a person is arrested or convicted of a DUI in California or any other state. It is also the form that one needs to provide to the DMV in order to obtain a restricted license. There are other cases where an SR-22 proof of insurance is needed to get a driver's license returned, such as if you have gotten your license restricted due to "Wet reckless" driving; if you have had too many accidents in a short time period; or, if you have an at-fault accident while driving without insurance.
The SR-22 form is similar to the DMV's SR-1 form. Both are forms that you can obtain from the Department of Motor vehicles. The difference is that SR-1 forms are used when you have an accident or are ticketed for not having or failing to show insurance proof. Do not use the SR-1 form if you have a DUI, are in a program, and have to show your proof of insurance - that is what the SR-22 is for.
The DMV will not accept any other form of documentation such as the policy itself, or an insurance identification card. It will only accept the SR-22 form. If you are trying to obtain a restricted license, you must provide the DMV with three things: the SR-22 form, which is your insurance proof, a $125 license re-issue fee, and proof of enrollment in a DUI program that has been approved by the DMV.
Additionally, for those who have been convicted of a DUI and are attending a DUI school, if four months have not passed by the time the DMV gets the notice of your conviction from the court, the requirement to show form SR-22 to the DMV becomes necessary.
It is important that you maintain proof of insurance for three years after the end of the four month suspension period. If you do not get dropped by your insurance carrier over this three year period or cancel your policy, then this proof of insurance will remain active. It is important that your insurance policy stays active because then the SR-22 will stay in effect.
If for some reason your insurance provider cancels your policy or something happens and you no longer have the insurance, your insurance provider is required to and responsible for notifying the DMV. The DMV will then contact you and let you know the deadline to file another SR-22 form. If you do not do this then your license will be suspended. It is important to carry the SR-22 with you for the amount of time specified.