I think if there is any kind of deformity like cracking in the car seat, it needs to be replaced. I know that Britax has some foam inserts that can be replaced if they are damaged. Maybe call your local fire dept. to find out the criteria.
I was curious, so I found the FAQ answer on Britax's web site. They say that you don't need to replace the seat for a "minor accident." They have a list of criteria for a "minor accident."
Re: When do you replace a carseat?
I was curious, so I found the FAQ answer on Britax's web site. They say that you don't need to replace the seat for a "minor accident." They have a list of criteria for a "minor accident."
https://www.britaxusa.com/customer-service/faq/after-a-crash
Here is a link to NHTSA's position on replacing seats after minor crashes.
https://www.nhtsa.gov/people/injury/childps/childrestraints/reuse/RestraintReUse.htm