The leaked memo revealed on Thursday that the government believes the UK will crash out without a deal on October 31, given Prime Minister Boris Johnson's demands that the Irish backstop be dropped from Theresa May’s Withdrawal Agreement.
The leaked document reportedly said that while a change in Mr Johnson's "hard negotiating position" is unlikely, he may use the upcoming G-7 summit in France to announce a breakthrough or collapse in talks with Brussels.
German officials also consider the EU's preparations for this eventuality to be "largely completed”.
The document calls for the EU's 27 remaining member states to toe their current line, which rules out renegotiating the deal reached with Mr Johnson's predecessor Mrs May.
However, a German government spokesman said on Friday that a no-deal Brexit is in no one's interest, adding that an orderly Brexit remains to be the government's policy.
The finance ministry declined to comment on the report.
It comes as Mr Johnson said Britain must leave the bloc on the October deadline “deal or no-deal".