German car number plates (Kfz-Kennzeichen) show the place where the car carrying them is registered. Whenever a person changes their main place of residence in Germany, or buys a new car, they are required to buy new number plates. Number plates can be bought which are valid all year round or between 2 to 11 months within any 12 months.

    The present number plate format, used since 1994, uses black print on a white background and first provides information about the country where the car is registered within the European Union. German license plates show a D (for Deutschland=Germany) on the blue strip on the left, which shows the European Union's flag, 12 golden stars in a circle on blue ground.
    The number of letters in the city/region prefix code mostly reflects the size and location of the district: the largest German cities generally only have one letter codes (B=Berlin, M=München (Munich), K=Köln (Cologne), F=Frankfurt), most other districts in Germany have two or three letter codes.
    Various combinations that could be considered politically unacceptable — mainly due to implications relating to Nazi Germany — are disallowed or otherwise avoided. The district Sächsische Schweiz uses the name of its main town, Pirna, in its code PIR, to avoid the use of SS, the name of the paramilitary organization; similarly SA is also unused. This is why cars in service for the government and parliament in Saxony-Anhalt are registered with LSA (Land Sachsen Anhalt). In 2004 in Nuremberg, a car owner was refused a number plate beginning N-PD because of the connection to the political party, the NPD.

Cited Wikipedia: http://en.wikipedia.org/wiki/German_car_number_plates