when do points get applied

[Blue123]

an alleged driving offence 18 months ago - went to trial, found guilty - 3 points given - when are these pointes dated from - the date of the alleged offence or the date of the hearing?

[PallasAthena]

Depends what the offence is, could be either. The government's explanation is here:

Penalty points (endorsements): How long endorsements stay on your driving record - GOV.UK (www.gov.uk)

[HandyAndy]

The government website information concerns how long an endorsement stays on your driving record.

For he purpose of "totting up", the penalty points count from the date of the offence. They will be no longer valid for "totting up" three years after that date. So in your case they will "expire" in about eighteen months time.