V-なくてはいけません

もう行(い)かなくてはいけません。

Mō ikanakute wa ikemasen.

I have to be going.

In speech this shortens to 行かなきゃ or 行かなくちゃ

宿題(しゅくだい)をやらなくちゃ。

Shukudai o yaranakucha.

I have got to do my homework.

The contracted form is for people you know well

早(はや)く寝(ね)なくちゃ。

Hayaku nenakucha.

I ought to get to bed.

The contraction is common even talking to yourself