Try to negotiate hard with the insurance company. The negotiations depends on various factors -
1- Who is at fault
2- Evidence available about accident
3- Car condition after accident (repairable/non repairable)
4- Garage Estimate (more than or equal to IDV)
5- Surveyor's report (observations made by the surveyor)

Sometime it's hard to get the entire amount/IDV - because there are so many riders etc. So always Try & negotiate - ask for detailed calculations before agreeing on anything etc.

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