You could be sued for defamation if you publish false material online which:
► seriously harms an individual's reputation
► causes an individual to be shunned or avoided
► exposes an individual to hatred, ridicule or contempt
► lowers an individual in the eyes of right-thinking people
► disparages an individual in their office, trade or profession
You also risk defaming an individual if you repeat defamatory material previously made or published by others. This might be by sharing a defamatory Facebook post or retweeting a defamatory tweet, for example.
Deleting defamatory material does not prevent a claim as it may have been published elsewhere.
If you are sued for libel (defamation by the written word) or slander (defamation by the spoken word), you could use a defence outlined in the Defamation Act 2013. One of the defences is 'truth', where you would need to prove the published material is true.
A claimant would be required to show that the defamatory material can be reasonably understood to refer to them – even if they are not specifically identified.
IN SHORT: Avoid publishing material online unless you know - and would be able to prove in court - that it is true.