書いてない

haven't written, haven't been writing

→ 書く
書い to write + て Te-form (conjunctive form) + ない Negation
verb · informal Rare #24,412
haven't written, haven't been writing Colloquial contraction of 書いていない.
JA: まだ何も書いてない。
EN: I haven't written anything yet.
Conjugation of 書く
Indicative
書かない書いてない

「お前が洗ってるリンゴ、俺の」「お前の?名前書いてないけど」

“That apple you’re washing is mine.” “Yours? Your name isn’t written on it.”

書いてないんです

I haven't written it.

— いまを生きる (1989)

まだトムに手紙書いてないんだ。

I haven't written to Tom yet.

何も書いてないんだろう?

You didn't write anything, did you?

— 鏡 (1975)

いや、書いてないよ。

No, I didn't write it.

壁が崩壊して以来書いてないと聞いた

I heard you haven't written since the wall collapsed.

— 善き人のためのソナタ (2006)

何も書いてない

There's nothing written.

— アメリ (2001)

私の筆跡に似てるけど、私は書いてないよ。

It looks like my handwriting, but I didn't write it.