Wiktionary
on the same page
adv. (context idiomatic English) In broad agreement or sharing a common general understanding or knowledge (common in office environments).
Usage examples of "on the same page".
If nothing else, it's one way of making sure we and our allies are on the same page when we discuss military options, and the fact that they're completely familiar with our doctrine helps eliminate a lot of potential confusion from joint operations.
Even so, things usually wash up, or get discovered in some marsh grass or something, but that's when everybody's on the same page.