The age identifier changes twice a year, in March and September. To distinguish between these two six monthly changes they have been allocated different number sequences. The following table shows how this will be achieved:

Year: March September
2001 - 51
2002 02 52
2003 03 53

The use of the figure 5 to precede the year, for September registrations, will maximise the registration mark combinations and offer a long-lasting system. The 5 will change to 6 in 2010 and to 7 in 2020 and so on until 2050 when the format may be reversed to extend the format another 50 years.