What it means
A little throat-clearer you chuck in before stating something you reckon is obvious or already understood. Often used in rules or reminders, and half the time it’s said with a wink because you’re literally about to say the thing. Can sound polite, mildly smug, or passive-aggressive, like you’re teaching basic manners to someone who should know better.
Usage examples
"It goes without saying, but if you’re using the loo, replace the bog roll. Dad’s written a note again, like we’re flatmates, not family."
"It goes without saying that you tidy up after yourself."
"Good food, great company, and it goes without saying, plenty of wine."
"It goes without saying, but if you nick the last biscuit, put some back on the shop list."
"Lovely night, solid tunes, and it goes without saying, Kev turned up late with chips."
Where it comes from
This one’s been in English for centuries and is generally traced to a calque of French ça va sans dire, literally the same idea in slightly fancier clothes. It kept that neat little knowing vibe, where you signal something’s obvious while cheekily going ahead and saying it anyway.