Because maintaining an affair requires expenditure, some people choose to use hidden bank accounts instead of trying to hide expenditures in shared bank accounts. It is much easier to simply open a checking account that you can use to make all of your purchases, than to keep hiding those purchases from someone who has access to that account. You should also be aware of secret accounts that may be opened to siphon money away in preparation for a partner separating from the relationship. You may have to do some detective work to identify these accounts. One of the easiest ways is to simply purchase a background check or credit check on your significant other.