Even though people know it can ruin relationships, couples still lie about money. The American Institute of Certified Public Accountants surveyed 1,000 adults and found three in 10 who are married or living with a partner admit to financial infidelity, from hiding purchases to buying big-ticket items without discussing it first. Some 7% of respondents have kept a work bonus or lottery winnings secret and 4% have hidden savings or retirement accounts. Of all the reasons couples fight, 27% said they fight about money more than any other issue, including children and work. To keep financial peace, the report suggests couples fully disclose their credit card statements, credit reports and bank accounts. Splitting the financial responsibilities could help keep a sense of balance, the report added.