No, insurance companies do not post-date insurance policies. Backdating the effective date is not permitted. If an insurance carrier would backdate the start date of a policy this would inevitably favor the insured, because it opens the insurance company to risk. For example a person could have been in an accident during this time and though they did not have insurance now try to claim it if the insurance was post-dated. 

If you need car insurance for your vehicle, even though the effective date cannot be backdated to September 15, you can get a quote here with us.