DR40 offence code is used by the DVLA for an offence of being drunk in charge of a vehicle whilst over the prescribed limit. This carries a minimum of 10 penalty points or a minimum period of disqualification (no minimum period).
Codes DR40 to DR70 must stay on a driving record/licence for 4 years from the date of the offence or 4 years from date of conviction where a disqualification is imposed.
More information can be found on the DVLA website
here.
When a conviction becomes spent under the Rehabilition of Offenders Act 1974 is a slightly different question.
An endorsement for a road traffic offence listed in Schedule 2 to the Road Traffic Offenders Act 1988, imposed either by the court or by means of a fixed penalty notice (FPN) is a sentence for the purposes of the 1974 Act and may become spent after 5 years (or two and half years where the offender is under 18). Road traffic legislation specifically provides for a FPN in these circumstances to be treated as a conviction and dealt with as such under the 1974 Act. Penalty points and a driving disqualification imposed by the court on conviction may become spent when they cease to have effect (penalty points have effect for three years as set out in road traffic legislation). Where the court imposes more than one sentence or penalty for the offence then the longest rehabilitation period determines when the conviction may become spent.
So, in your case (and assuming that you are an adult) your sentence imposed by the court included a fine (rehabilitation period 1 year), an endorsement (rehabilitation period 5 years), and a driving disqualification for 4 months (rehabilitation period 4 months); the rehabilitation period for this conviction (that is the the time that must pass before the conviction is "spent") under the Rehabilitation of Offenders Act 1974 will be 5 years because the endorsement carries the longest rehabilitation period.
If you were under 18 different rehabilition periods apply and, the conviction may become spent after 2 and a half years because the endorsement would become spent after this reduced period in the case of a juvenile.
Once the conviction becomes spent, the person is not required to declare it when applying for most jobs (unless you are specifically told that the Rehabilition of Offenders Act does not apply or are specifically asked to disclose spent convictions), or (motor) insurance.
