Japanese phrase
___は結構です。 ___ wa kek kō de su
Meaning
I don't need ___.
When to use it
Politely refuses something that has been offered. It is common in shops and restaurants, though the tone can sound firm depending on the setting.
Example dialogue
レジ袋をお付けしますか？ re ji fukuro o o tsu ke shi ma su ka
Would you like a shopping bag?
袋は結構です。 fukuro wa kek kō de su
I don't need a bag.