Filing a claim during the collision repair is typically initiated by a phone call to either your body shop or your Insurance Company. Both insurance companies talk then hash it out to see who's going to pay for the repairs. After they decide who's responsible, the claim is either approved or denied.
The repair process begins with an estimate. Remember, just because the adjuster or body shop has written an assessment, it doesn't mean the claim is approved.
Insurance companies like to send out an adjuster before body shops begin their work. They typically pay the claim based on the initial estimate written by the adjuster; body shops will match most Insurance estimates.
After the Insurance company approves the work, the body shop will typically generate a supplement after the work has begun.