The new numbers will identify where a car was bought
New cars now have a letter indicating the city they are from, numbers which represent the six-month period in which they were registered, and three random digits at the end.
The authorities say the plates will be easier to read, not least by speed cameras.
But recent surveys have suggested that few people understand the new system.
Changing times
Since the early 1960s, the age of a car has been indicated by a letter displayed at the beginning or end of the number plate.
But this system has been abandoned in favour of the new code which includes seven symbols, such as AB51 CDE.
The first two letters show where a car was registered, while the numbers indicate the age of the vehicle and whether it was bought in September-February or March-August.
The last three letters are random.
Under the new system, a car bought in the Ipswich area between now and next March, would carry a plate beginning with AV, AW, AX, or AY.
The next two numbers would be 51, with 5 indicating a September-March period purchase and 1 representing the year (2001).
The same car bought next March would feature a plate with the numbers 02, with 0 showing the vehicle was bought between March-August, and 2 for the year 2002.