My OH has received a FPN this morning (sigh!) I have just been online to pay it and it asks for the FPN reference number. I've tried all variations of what is on there, but it keeps saying 'invalid number'. Could it be that the notice hasn't been processed and I'm too eager tp pay it?
Possibly...
You will have a designated period in which to pay, no urgency if it came today.
See if it works tomorrow and if not is there a contact number/helpline.