end of year write off, page-3

Since the Administrators have now declared that the shares are worthless, they also mention:

"As a consequence, shareholders who acquired the shares on or after September 1985 may choose to make a capital loss in the income year that includes the date of declaration as a result of CGT event G3 occuring. The capital loss is equal to the reduced cost base of the shares".

Use of the word 'may' suggests to me that you can declare the loss this year or you may choose to declare it next year. Is that how other people see it ? Or MUST you declare the loss this year ?