This means you must do something. It shows that an action is needed. You have to do it.
Verb [ない-form] + と + いけないPrimary
This means you must do something. It shows that an action is needed. You have to do it.
そろそろ寝ないといけない時間だ。
It's about time I have to go to sleep.
昨日は図書館に本を返しに行かないといけなかった。
Yesterday, I had to go to the library to return a book.
レポートを提出しないといけないから、今夜は徹夜かもしれない。
Because I have to submit my report, I might have to pull an all-nighter tonight.
全部一人でやらないといけないことはないよ。手伝うから言ってね。
It's not that you have to do it all by yourself. I'll help, so just let me know.
会議の前に、この資料を読んでおかないといけない。
I have to read these materials before the meeting.
This phrase means you need to do something because of a specific situation. It is like saying, "I have to go now to catch my bus." It is not for general rules, like "Everyone must pay taxes."
This is a common way to say "must do". It is less formal than "〜なければならない". That form is for writing or formal talks. This is the plain form of "〜ないといけません". That is for polite speech. "〜なくてはいけない" is very similar. But this form is used more often in daily talk.
Watch out: Many people mix up 'must do' and 'don't have to do'. Both use 'ない'. '〜ないといけない' means 'if you don't do it, it's bad'. So, you must do it. '〜なくてもいい' means 'even if you don't do it, it's okay'. So, you don't have to do it.
Use this when you want to say you must do something. It is a short way to say "I have to." You can use it when you need to do something right away.
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