Some 23% of people who currently have a partner said they had done this, with the most common reason being to conceal the amount of debt they have, Lloyds Bank found.
For many, money has led to arguments, with more than a third (37%) of people having argued with their partner about cash, the survey of more than 2,800 people across the UK found.
And, in further evidence of a reluctance to discuss their own finances, people are nearly twice as likely to have discussed their thoughts on winning the lottery as they are to have talked about their own will, with 65% and 34% having done so respectively.
Meanwhile, a quarter (25%) of people have lied to family and friends about their personal finances, according to Lloyds, which has partnered with Relate to encourage people to talk about money at key life stages.
Nearly a third (32%) of people said they find it stressful talking about their finances with family and friends and two-fifths (43%) had felt embarrassed.
Despite the findings, three-fifths (61%) of people said they feel better when they talk about money concerns.
Professor Tanya Byron, consultant clinical psychologist and Relate patron said: “Feelings about money can be strong, but conversations about money - even difficult ones - don’t have to lead to arguments.
“Talking openly about money can help us take shared responsibility, strengthen our relationships, and protect our mental wellbeing.”
Lloyds’ M-word campaign has a series of courses to help people talk about money at key life stages, such as getting married or leaving home.