I had this quandary with my sons Alfa recently. I was determined not to tax it if not necessary. Let's face it if you do the deal on say 3rd of the month, the road Tax has been paid for all that month, and the old keeper will not get refunded for the remaining 27 days of the month.
This is what happened with the Alfa, so I kept checking on "is my car taxed" everyday. It took 14 days to be recorded as "not taxed". As soon as it flagged up, I taxed the car, so effectively the DVLA were paid twice for this month. Bet this makes them a few quid over a year
