The night of Tuesday August 9 was meant to be the chance for every Australian to be counted, with the federal government confident moving the census online would proceed without a hitch.

But newly released Australian Bureau of Statistics documents show a very different story.

A cascading series of emails released under freedom of information suggest seven years of planning didn't cover how staff should communicate or respond to a crash, with the subsequent meltdown culminating in Prime Minister Malcolm Turnbull's office intervening around 10pm.

Days of preparation are laid out, with early emails showing staff preparing social media posts, proofing screenshots and confirming plans for the hours ahead.