DD40 is Dangerous Driving.
This is a serious offence for which the maximum penalty is two years imprisonment and would certainly be shown on a CRB check.
Provided you were over 18 at the time of conviction, the �rehabilitation� period for somebody receiving a community penalty is five years and you must declare this offence when asked within that period. If you were under 18 the period is two and a half years. A conviction involving a driving ban becomes spent when either the period of the ban has expired or the period relating to the substantive sentence (in your case the community penalty) � whichever is the longer - has expired.
Some areas of employment are exempt from the Rehabilitation of Offenders Act. The main exceptions are jobs working with children or vulnerable adults, certain posts in areas of health, pharmacy and the administration of justice, senior positions in the finance industry, and jobs involving national security. In these cases all convictions, whether spent or not, must be disclosed.