It is not a question of bad grammar, just dialect.
それは文法的間違いではなく，単に方言の問題だ
It is not always fully appreciated that ...
…ということは必ずしも十分に理解されていない
It is not as [so] difficult a question as you might think.
思っているほど難しい問題ではない
It is not certain that we will arrive on time.
時間通り着けるか定かではない
It is not decent to speak ill of others behind their backs.
陰口をきくのはよくない
It is not in his nature to attack anyone.
彼はだれかを攻撃するような人ではない
It is not news that energy consumption is growing.
エネルギー消費が増大しているというのは今さら耳新しいことではない
It is not particularly surprising.
別に驚くことでもない
It is not proper 「for you to talk that way [that you (should) talk that way].
そんな口のききかたをしてはだめだ
It is not red, but black.
赤ではなくて黒い
