Way 1 · best default
It slipped my mind
You forgot, but not on purpose. Softer than a plain "I forgot".
Examples
Sorry, it slipped my mind. I'll send it now.
I meant to call you on your birthday, but it slipped my mind.
In a conversation
A: Did you book the table?
B: Oh no, it slipped my mind. I'll ring them now.
Common mistake
Not: It slipped out of my mind.
Say: It slipped my mind.
No "out of". The thing slips your mind, like it slid away by itself.
