Use 没有 (méiyǒu) to negate past actions (to say that someone didn't do something, or something didn't happen).

Structure

Usually verbs can be negated with 不, but that construction is used for habitual or present actions. If the verb is about an action in the past, though, 没有 should be used:

Subject + 没有 +  Verb

Examples

Note that you can shorten 没有 to just 没:

Remember that 了 is not used with 没有. 了 marks completed actions, whilst 没有 is used for actions that didn't happen. These two don't work together. This is a very common mistake for Chinese beginners, so be sure to be attentive to it.