Japanese 334 - Have to do - 〜なくて は いけない

You've already learnt that you can express that something must be done with the phrase ない と いけない.

You can say exactly the same using the phrase 〜なくて は いけない. The only difference is that 〜なくて は いけない is slightly more formal and a bit more emphatic, so it might be slightly stronger in conveying the sense of necessity.

You can use いけません instead of いけない to make the sentence a bit more polite and formal.