I was in a car accident the other day and I was wondering if you could have insurance on a car that's not registered?

How did you come to have a car that's not registered? Can you provide more?

I am assuming, you do not have a current tag, or have it registered for the current year, But yes you may have insurance on a car that you don't even own if you don't tell the insurance company, you just give them the car serial number.

But most people who have not gotten their current tags ( not a few weeks late but just don't have them) normally don't have insurance either.

It was the other person's car that was not regestered and it wasn't regestered since November

There is a possibility that they had insurance on the car before the registration expired in November, and perhaps they just forgot to renew the registration. Did they get a ticket for the registration being expired? In NY the DMV sends out renewal forms, but maybe in your state they do not & you have to remember to renew the registration without the DMV sending the forms. Or maybe they got the renewal & never got around to renew.

There shouldn't be a problem making a claim against the other insurance company if their driver was at fault. I am not sure if there is any language in the policy that would give the insurance carrier the right to deny coverage due to this situation.