Something like this...

Select NIN_CODE,Count(*) as Cnt from (

select distinct OO.ORDER_NUMBER, OO.NIN_CODE

from Table as OO

WHERE (OO.SUBMITTED_DATE BETWEEN '20090101' AND '20091231')

AND (OO.TICKET_NUMBER IS NOT NULL) and OO.NIN_CODE='990685711' or OO.NIN_CODE='993435940'

) Main

group by NIN_CODE