The new system is supposed to prevent someone purchasing a taxed vehicle and driving it uninsured.
From what I understand, for the first month, the ANPR system does not automatically pick up vehicles whose tax has run out, although if anyone manually checks the vehicle, it will come up as being untaxed.
When a vehicle is purchased it will show on the system as being taxed, until the paperwork is processed. As soon as the paperwork is processed, it will show as being untaxed from the date of purchase.
If the vehicle is purchased in the middle of a month, the new keeper will have to pay from the beginning of that month, and the old keeper will receive a refund from the end of that month. The Government will make an extra month of tax.
However it is possible for the new keeper to pay from the beginning of the next month, though the system will show that the new keeper should have paid from the beginning of the previous month. It is then up to someone at DVLA to decide whether a fine should be issued
If you do not receive a tax/sorn reminder and a fine is issued, the DVLA will inform you that it is not their responsibility if you do not receive it.
By the same token, if you pop ÂŁ80 cash into an envelope to pay the fine and DVLA do not receive it, it's not your responsibility if DVLA do not receive it.