How to Say “Must” and “Don’t Have To” in Japanese
To say “must” or “have to” in Japanese, use the negative form of the verb plus a phrase that means “it won’t do”: 行かなければならない, 行かなくてはいけない or 行かないといけない all mean “I have to go”. In casual speech these shrink to 行かなきゃ and 行かなくちゃ. To say “don’t have to”, use なくてもいい (行かなくてもいい, “I don’t have to go”), and to say “must not”, use てはいけない (行ってはいけない, “you must not go”). This guide shows how each form is made, how formal it sounds and which one to use.
How to make the “must” forms
Start from the ない form of the verb, drop the い and add the ending. See Japanese verb conjugation basics if the ない form is new.
| Form | Example (行く, to go) | Feel |
|---|---|---|
| 〜なければならない / なりません | 行かなければなりません | Formal, common in writing, rules and announcements |
| 〜なくてはいけない / いけません | 行かなくてはいけません | Neutral, common in speech |
| 〜ないといけない / いけません | 行かないといけません | Neutral and very common in conversation |
| 〜なきゃ (いけない) | 行かなきゃ | Casual, with friends and family |
| 〜なくちゃ (いけない) | 行かなくちゃ | Casual, slightly softer |
なければならない and なくてはいけない are close in meaning. Textbooks sometimes say ならない is for general rules and いけない for personal obligations, but in everyday speech people mix them freely. The bigger difference is formality: in a meeting, もう帰らなければなりません sounds polite; with a friend, もう帰らなきゃ is natural.
Adjectives and nouns
- い-adjectives: 安くなければならない (it has to be cheap)
- な-adjectives and nouns: 静かでなければならない (it has to be quiet), 日本人でなくてもいい (you don’t have to be Japanese)
“Don’t have to”: なくてもいい
Use the ない form, change ない to なくて, and add もいい: 明日は来なくてもいいです (You don’t have to come tomorrow). なくても大丈夫です is a softer, very common version. In polite questions: 予約しなくてもいいですか (Is it OK not to book?). The answer is often はい、大丈夫です.
“Must not”: てはいけない
Use the て form plus はいけない: ここで写真を撮ってはいけません (You must not take photos here). In casual speech this becomes ちゃだめ: 触っちゃだめ (Don’t touch). On signs you will often see 〜禁止 (prohibited), such as 撮影禁止 (no photography). For permission, the positive version is てもいい: 写真を撮ってもいいですか (May I take a photo?).
Using these at work
At work, a direct しなければなりません about someone else can sound bossy. Japanese speakers often soften obligations with phrases like 〜していただく必要があります (we need you to…) or 〜していただけますか (could you…?). See casual vs polite Japanese and keigo basics for work.
Common mistakes
- Using the dictionary form instead of the ない form: 行けなければ is wrong, 行かなければ is right.
- Mixing up なくてもいい (don’t have to) and てはいけない (must not). One is permission not to do something, the other forbids it.
- Using なきゃ with your boss. Keep it for friends.
For more grammar, see Japanese conditionals and the te-form.
Practise in conversation
These forms come up every day, so they’re worth practising until they’re automatic. Our native Japanese tutors teach one-to-one online, in English, and can give you real situations to practise them in, from house rules to work tasks. Your first 15 minutes are a free trial.