Were you speeding?
Are you the registered keeper?
Was he stopped at scene?
You can't reject a NIP. At least, you can. Then they will charge you with failing to identify.
Because the S172 request is stand alone.
What you can do is comply with S172 responsibilities and then if they prosecute try to argue that the prosecution is defunct because they were out of time.
There is quite a lot of case law that says that the 14 day period begins the day after the incident so that it is a complete 14 days.
On my calculations though they are still one day out of time.
But you have to go to court to argue that.
Quite often as long as they receive a S172 form back they will not summons though.
They will offer a fixed penalty as that is easy for them to do. The question will be whether if rejected they would summons.
Obviously though then you are taking a risk.
Can I clarify anything for you?
There is an exemption but it doesn't apply here unless there were problems at the DVLA.
No, it should have been despatched within 14 days.