ことはない

Expresses that there is no need to do something. It is typically said to reassure or advise the listener that an action or feeling is unnecessary.

Common in conversation when reassuring, comforting or advising someone that an action or worry is unnecessary. It is often reinforced with 何も or そんなに. Compared with なくてもいい, it sounds more emphatic and often carries the speaker's feeling that the action is pointless or uncalled-for.

• なくてもいいN4「なくてもいい」has a mild, gentle tone and mainly means 'it's fine not to do it,' with only a weak sense of reassurance; it also attaches to adjectives and nouns, and can be used to ask 'is it okay not to...?' 「ことはない」attaches only to the dictionary form of verbs and carries a stronger note of reassurance.
• までもないN1「までもない」also means 'no need to,' but it centers on objective judgment: the matter is obvious or a simpler way exists, so going out of your way to do it is pointless; its sense of reassurance is weak. It also has adverbial and attributive uses such as 「言うまでもなく」.
• には及ばないN1When it means 'no need to,' 「には及ばない」is interchangeable with 「ことはない」, but its tone is solemn and formal; besides the dictionary form of verbs, it can also attach to action nouns. It has the additional sense 'can't measure up to,' which 「ことはない」does not have.
• にあたらないN1「にあたらない」is a written-language expression with a stiff, judgmental tone; it attaches only to reactions or evaluations such as surprise, worry, blame, and praise, and can also take nouns like 「非難」. Concrete actions like 「来る」can only take 「ことはない」.
• ものではないN2「ものではない」has two uses: first, it admonishes on the basis of common sense that one 'shouldn't do...,' with a preachy tone; second, it means 'there's no way one could...' and can attach to the potential form. 「ことはない」only says 'there's no need' and serves to reassure rather than prohibit, so the two cannot be interchanged.
• べきではないN3「べきではない」judges on principle that one 'shouldn't do...,' carrying an admonishing, critical tone; its past form can express regret, and it also attaches to adjectives and nouns. 「ことはない」only says 'there's no need' and serves to reassure—sometimes both fit the same sentence, but with different meanings.

Like なくてもいい it says something is unnecessary, but ことはない is more emphatic and reassuring, while までもない (too obvious or trivial to need doing), には及ばない (formal, polite 'no need') and にあたらない (not warranted, usually with 驚く or 非難する) are more formal N1 expressions. Unlike ものではない (a social norm: 'one shouldn't') and べきではない ('should not'), ことはない does not forbid anything; it only denies the need.