In ALL cases a Notice of Intended Prosecution will have been issued to the last known keeper of the vehicle (obtained from DVLA records) within 14 days of the alleged offence; safeguards are in place to prevent documentation being sent outside this statutory period.
If you have received a Notice outside the 14 day period you are likely to have been nominated as the driver and now have a responsibility to respond to the S172 request for information within the time specified on the Notice.