it's nothing; don't mention it; no thanks necessary
A polite, somewhat formal phrase used to decline thanks or a gift, implying that the favor was trivial. Often used in response to expressions of gratitude.
See also: 礼には及ばない
"Thank you for helping me." "It's nothing."
お礼には及びません。当然のことをしたまでです。
No thanks are necessary. I only did what was natural.
From お礼 (thanks) + には (particle) + 及びません (polite negative of 及ぶ, 'to reach, to be necessary'). Literally 'it does not reach the point of thanks'.