From Longman Dictionary of Contemporary Englishmake no mistake (about it)make no mistake (about it)spokenEMPHASIZE used to emphasize that what you are saying is true, especially when you are warning about something serious or dangerous Make no mistake, this is the most serious threat our industry has ever seen. → mistake
Examples from the Corpus
make no mistake (about it)• Make no mistake about it - I am not going to put up with this anymore.• And make no mistake about it, she knew I was there.• And make no mistake, the family works overtime to make its instructions felt.• And make no mistake, there will be plenty of bets.• The Pinot Noirs from Burgundy are often expensive, make no mistake.• In the second 250 race Robert made no mistakes, leading all the way to win from McCallen and Coulter.• I tried to make no mistakes, but they called me naughty every moment of the day. 