To describe what you do not need to do,
take a negative sentence in the short
form, drop the final い - i of ない - nai,
and add くともいいです -
nakute mo ii desu. なくて - nakute is the negative
te-form.
靴を脱がなくてもいいです。
You do not need to take off your shoes.
kutsu-o nuganakute mo ii desu.
プレゼントは高くなくてもいいです。
The present does not need to be expensive.
purezento-wa takaku nakute mo ii desu.
~ない -> ~なくてもいいです
~ not -> ~ /not be/ /also/ good is (does not
need to...)